Gastropoda with shells Key:

Key to Gastropoda with Shells

Taken primarily from Kozloff, 1987, 1996 p. 192 (Copyright 1987, 1996, University of Washington Press. Used in this web page by permission of University of Washington Press)

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Lower taxonomic level Main Page Alphabetic Index Systematic Index Glossary

1a Shell permanently cemented to a hard substratum (usually rock), coiled loosely or irregularly and generally twisted, resembling the calcareous tube of a serpulid polychaete more then a snail shell (picture) (picture) Family Vermetidae

1b Shell not permanently cemented to a hard substratum, either tightly coiled or tubular, conical, or cap-shaped 2

2a Shell tubular, conical, or cap-shaped, without obvious coiling 3

2b Shell obviously coiled, although the spire may be short 9

3a Shell tubular, slightly curved, the height more then twice the diameter Family Caecidae

3b Shell conical or cap-shaped, the height rarely exceeding the greatest diameter (photo) 4

4a Shell with a dorsal opening at or near the apex (photo) (photo), or with a slight indentation at the anterior margin (such an indentation is present only in the rare and subtidal Arginula bella; it marks the place where a groove on the interior of the shell, beginning at the apex, reaches the margin) Family Fissurellidae

4b Shell with neither a dorsal opening at or near the apex nor an indentation on the anterior margin 5

5a Interior of shell with a shelf (photo) (photo) Family Calyptraeidae

5b Interior of shell without a shelf (photo) 6

6a Apex of the shell usually at or anterior to the middle, sometimes slightly posterior to the middle (if only the shell is available, the open end of the horsehoe-shaped muscle scar faces anteriorly (photo), except in the family Siphonariidae, in which the open end of a nearly C-shaped muscle scar faces the right side [left side, if the shell is observed in ventral view]) 7

6b Apex of the shell decidedly posterior to the middle (at least as far as the beginning of the last quarter) (the foot secretes a calcareous base, and the animal remains attached to this) Family Hipponicidae:
Hipponix cranioides

7a Outline of the shell, in dorsal view, not symmetrical, the apex slightly to the right of the midline; muscle scar (often indistinct) nearly C-shaped, its open end facing the right side (left side if the shell is observed in ventral view); with a shallow siphonal groove passing through the open end of the muscle scar Subclass
Pulmonata,
Family Siphonariidae

7b Outline of the shell, in dorsal view, symmetrical (unless deformed by an injury) (photo), the apex on the midline; muscle scar horsehoe-shaped, its open end facing anteriorly (photo); without a siphonal groove 8

8a Interior of shell uniformly whitish, without any color pattern; apex in the anterior third of the shell; exterior with rather conspicuous concentic lamellae (subtidal) Family Lepetidae

8b Interior of shell usually with a color pattern of some sort (a blotch in the apical region, marginal markings, etc.) (photo); apex in the anterior or middle third of the shell (in the middle third in Acmaea mitra, the only species in which the interior is uniformly white); concentric lines not often conspicuous Order
Patellogastropoda,
Families Acmaeidae,
Nacellidae,
and Lottiidae

9a Abalones--shell low and earlike, with a low spire near the posterior end, and with a series of holes (some closed) near the left side; length sometimes exceeding 10 cm (picture) Family Haliotidae

9b Shell generally not low and earlike (except in Lamellariidae and Velutinidae), and without a series of holes near the left side; only a few species larger then 10 cm, and nearly all of these have tall spires 10

10a Shell (completely or almost completely internal in Lamellariidae) with a low profile, thus resembling the shell of a abalone (photo) 11

10b Shell not resembling that of an abalone 12

11a Shell thin, translucent white, and completely or almost completely internal Family Marseniidae

11b Shell rather firmly calcified, covered by an almost velvety periostracum, and to a large extent external (photo) Family Velutinidae

12a Outer lip of the aperture with a deep slit ( the shell, which has a short spire above the proportionately large body whorl, resembles that of a Margarites or Lirularia [Trochidae], its diameter being about equal to its height; found only at depths greater then 400 m) Family Scissurellidae

12b Outer lip of the aperture without a deep slit (there may, hovever, be a notch or distinct siphonal canal at the anterior end of the aperture, and there may also be a slight notch on the outer lip near the posterior end of the aperture) (includes most intertidal and subtidal prosobranch gastropods, and some opisthobranchs and pulmonates) 13

13a Length of the aperture nearly equal to the height of the shell (if there is a spire, it is not raised) 14

13b Length of the aperture not nearly equal to the height of the shell (there is a raised spire) 15

14a Shell thick, similar in shape to that of a cowrie, with a series of teeth on the inside of the outer lip of the aperture; aperture not decidedly wider in its anterior half than elsewhere; height about 3 mm Marginellidae:
Granulina margaritula

14b Shell thin, not resembling that of a cowrie; without teeth on the inside of the outer lip of the aperture; aperture usually widest in its anterior half; height up to nearly 2 cm, but much smaller in some species Subclass Opisthobranchia,
Order Cephalaspidea

15a Much of the periostracum in the form of conspicuous hairs or bristles 16

15b Periostracum not in the form of conspicuous hairs or bristles 17

16a With a prominent siphonal canal that is about 1/3 the total length of the aperture (photo); height up to about 12 cm (or more) Cymatiidae:
Fusitron oregonensis

16b Without a distinct siphonal canal, but the anterior of the aperture is angled in such a way that it forms a small spout; height generally less than 4 cm Capulidae
(formerly Trichotropidae)

17a Anterior end of the aperture without a distinct siphonal notch, spout, or canal (photo) 18

17b Anterior end of the aperture with a distinct siphonal notch, spout, or canal 34

18a Interior of shell pearly (except in Halistylus pupoideus, family Trochidae); with an operculum (photo) 19

18b Interior of shell not pearly (it may, however, be colored); with or without an operculum 20

19a Operculum thin and horny, with numerous spiral lines (photo) Family Trochidae

19b Operculum calcified and rather thick, with only a few spiral lines Family Turbinidae

20a Diameter of the shell much greater than the height (aperture almost circular, equal to about half the total diameter, which does not exceed 4 mm; without periostracum) Vitrinellidae:
Vitrinella
columbiana

20b Height of the shell equal to or greater than the diameter 21

21a Columella with 1 or more distinct folds or ridges; height less than 1 cm 22

21b Columella without any folds or ridges; height may exceed 1 cm 24

22a

22b

23a

23b

24a Diameter about equal to the height; shell generally almost globose, consisting mostly of the body whorl (umbilicus either conspicuously open or covered by an obvious callus; height of some species attaining 10 cm) Family Naticidae

24b Height decidedly greater than the diameter; shell not almost globose, the spire usually at least one-sixth of the total height 25

25a Height not more than twice the diameter 26

25b Height considerably more than twice the diameter 30

26a Umbilicus a slit between the columella and the body whorl (generally on eelgrass or on algae, especially kelps, mid- to low intertidal and subtidal) (formerly Family Lacunidae) Subfamily Lacuninae of
Family Littorinidae

26b Umbilicus absent or indistinct (in some species, there is a narrow space between the body whorl and the edge of the inner lip of the aperture) 27

27a Height commonly exceeding 5 mm, and in some species slightly exceeding 1.5 cm; operculum horny; periostracum not uniformly tan or brown (Almagorda subrotundata is brown, but usually has spiral banding) (mostly at higher tide levels on rocly shores, or on rocks, concrete and wood in bays, sometimes in salt marshes) Family Littorinidae

27b Height not exceeding 4 mm; operculum horny or calcareous; periostracum sometimes uniformly tan or brown (Assiminea californica, Assimineidae, inhabits salt marshes, but members of the other families to which this couplet leads are typically found at lower levels of rocky or gravelly intertidal areas) 28

28a

28b

29a

29b

30a Shell highly polished, in some species slightly bent; suturesbetween whorls so slightly indented that they are barely evident (whorls themselves, moreover, are nearly flat); parasitic on echinoderms, and strictly subtidal Family Eulimidae

30b Shell not usually highly polished, and not bent; sutures between whorls distinct; not parasitic on echinoderms (but the Epitoniidae are parasitic on various cnidarians) 31

31a Spire decidedly tapered and generally with more than three whorls; not typically found at higher tide levels in salt marshes 32

31b Spire scarcely tapered, and generally with only 3 whorls (the older whorls disappear and the uppermost surviving whorl is usually very short and smoothly rounded; typically at highter tide levels in salt marshes Truncatellidae:
Cecina
manchurica

32a Height of the spire shorter than the body whorl; spire usually with 4 or 5 surviving whorls; shell sculpture limited to prominent axial ribs, and when the shell is viewed with the aperture lowermost and facing the observer, the ribs are more nearly parallel to the left side of the shell than to the right side Rissoinidae:
Rissoina
newcombiana

32b Height of the spire considerably greater than the height of the body whorl; spire usually with at least 6 surviving whorls; shell sculpture sometimes limited to axial ribs, but if so, the ribs are more or less parallel to both sides of the shell 33

33a With both axial ribs and spiral ridges (the intersections of these sometimes form beads), or with spiral ridges only Family Turritellidae

33b Sculpture limited to axial ribs (except for a single spiral ridge near the base of the body whorl) Family Epitoniidae

34a Upper portion of the outer lip of the aperture with an anal notch
If the lip has been fractured, the contours of the growth lines nearest the lip are likely to indicate that an indentation had been present. In species that do not have a distinct anal notch, the following combination of characters may enable one to recognize them as members of this family; width of the aperture less than one half, and usually less than one third, the height of the aperture; prominent axial ribs; foot milky white. Presence of an anal notch, however, is the most reliable feature.
In certain species of Antiplanes, the shell is coiled sinestrally rather than dextrally, and this is helpful in assigning them to the Turridae. Most members of the family are subtidal and they typically inhabit soft sediments. None in our region is likely to be found in a rocky intertidal habitat. 53 Turridae

34b Upper portion on the outer lip of the aperture without an anal notch or trace of a notch 35

35a Shell highly polished, without any sculpture other then fine growth lines; widest part of the aperture (near its lower end) less then half the diameter of the shell (picture); operculum inconspicuous; typically in sandy substrata Family Olividae

35b Shell not polished, and usually with at least some sculpture; widest part of the aperture (generally near its middle) usually at least half the diameter of the shell; operculum usually conspicuous and large enough to close the aperture tightly (picture picture); not necessarily limited to sandy substrata 36

36a Lowermost portion of the body whorls including the siphonal canal, set off from the rest of it by a conspicuous groove that [may even] interrupt the axial ribs (photo) [though in Nassarius fossatus the axial ribs do not extend this far anteriorly on the body whorl]. Family Nassariidae

36b Lowermost portion of the body whorl not set off from the rest of it by a conspicuous groove that interrups the axial ribs 37

37a Shell with at least 8 distinct whorls, not counting 1 or 2 that may have been worn away at the apex (in specimens that have been abruptly worn down to 4 or 5 whorls, one can estimate, on the basis of the surviving portion of the shell, that about 10 whorls have developed; height not exceeding 4 cm 38

37b Shell with not more than 7 whorls, even if none appears to have been worn away, except in specimens whose hight commonly exceeds 12 cm 41

38a Siphonal canal half the total height of the aperture; axial ribs prominent, not forming beads where they intersect the faint spiral ridges Family Neptuneidae:
Exiliodea rectirostris

38b Siphonal canal less than half the total height of the aperture (photo); axial ribs and spiral ridges sometimes forming beads where they intersect 39

39a Siphonal canal short but obvious; spiral ridges distinctly (and sometimes conspicuously) beaded where intersected by the axial ribs (photo) 40

39b Siphonal canal barely evident; spiral ridges beaded in some species that have axial ribs, but not in the most common species (Bittium eschrichtii); which lacks axial ribs Family Cerithiidae

40a Siphonal canal narrow, directed toward the left at a nearly right angle to the long axis of the shell (as the shell is viewed with aperture lowermost and facing the observer) (photo); with about 12 axial ribs; height up to 3.5 cm; usually in salt marshes Family Batillariidae:
Batillaria attramentaria

40b Siphonal canal broad, directed to the left at about a 45 degree angle from the long axis of the shell; with at least 12 axial ribs (and sometimes more than 30); height not often exceeding 1 cm Cerithiopsidae

41a Shell either with axial ribs as well as spiral ridges, or with only spiral ridges 42

41b Shell with only axial ribs Family Volutidae

42a Shell sculpture limited to spiral ridges 55

42b Shell with axial ribs (these may be low and incospicuous, however) or thin axial lamellae (picture), as well as with spiral ridges 43

43a Axial ribs limited to the spire (the body whorl may have a few irregularly spaced grooves that are perpendicular to the spiral ridges, and young specimans of Searlesia dira, under 2 cm long, have axial ribs on the body whorl) (photo) 44

43b Axial ribs or lamellae extending to the body whorl, even though they may be less distinct on the body whorl than on the spire 45

44a Columella with 2-5 folds; periostracum light brown; spiral ridges faintly evident on the inside of the outer lip of the aperture; subtidal Family Cancellariidae:
Neoadmete modesta

44b Columella without folds; periostracum gray; dark lines in the furrows between spiral ridges of the body whorl visible on the inside of the aperture; intertidal and subtidal Family Buccinidae:
Searlesia dira

45a Axial ribs on the body whorl restricted to the upper half of it (if continued into the lower half of the body whorl, they become much less prominent) (photo) 46

45b Axial ribs distinct on at least much of the lower half of the body whorl, and as prominent as those on the upper half of the body whorl 49

46a With a series of folds on the inside of the outer lip of the aperture as well as on the columella Family Columbellidae
(in part)

46b Folds sometimes present either on the inside of the outer lip of the aperture or on the columella, but not on both 47

47a With folds on the inside of the outer lip of the aperture (these coincide with spiral ridges on the outside of the body whorl); without folds on the columella Family Fusinidae

47b Without folds on the inside of the outer lip of the aperture; with or without folds on the columella 48

48a Axial ribs rather sharp; with 2-5 (usually 2 or 3) folds on the columella Family Cancellariidae:
Admete gracilior

48b Axial ribs low and broad; without folds on the columella Family Neptuneidae:
Plicifusus griseus
(now Family Buccinidae,
Colus griseus)

49a Siphonal canal (measured from the angle in the outer lip of the aperture where the canal begins) one-third to one-half the total height of the aperture 50

49b Siponal canal decidedly less than one-third the total height of the aperture (picture) 51

50a Either with axial ribs and spiral ridges equally well developed and prominent, or axial ribs represented by thin lamellae and spiral ridges faint Family Muricidae

50b Axial ribs poorly developed in comparison with the prominent spiral ridges Family Neptuneidae

51a Axial sculpture consisting of thin, frillylamellae (photo); spiral sculpture, which may be obscured by the lamellae, consisting of 1 or 2 prominent ridges on each whorl (picture) Nucellidae:
Nucella lamellosa

51b Axial sculpture consisting either of fairly broad ribs or of wrinkles (these may be irregular and discontinuous), but not of frilly lamellae; spiral sculpture consisting of closely spaced spiral ridges 52

52a With 2 or 3 folds on the columella Cancellariidae:
Cancellaria
crawfordiana

52b Either with 1 fold or none on the columella 53

53a Without a fold on the columella; periostracum, if persistent, straw-colored or dark brown Family Neptuneidae
(in part)

53b With 1 fold on the columella; periostracum blackish or whitish 54

54a Periostracum blackish, thick, cracked, but otherwise more or less continuous except where the spire is eroded; inside of aperture purplish brown; axial ribs and spiral ridges about the same size; height up to about 2.5 cm; intertidal, in mudflats Nassariidae:
Ilyanassa
obsoleta

54b Periostracum whitish or dull brown; inside of aperture white or pinkish; axial ribs much more pronounced than the spiral ridges; height up to 7 cm; subtidal Family Buccinidae:
Buccinum spp

55a Columella with 2 or more folds 56

55b Columella without folds 57

56a Spiral ridges present over the entire shell; columella with about 5 folds; restricted to deep water Family Volutomitridae

56b Spiral ridges present only on the lowest part of the body whorl, near the siphonal canal; columella with 2 or 3 folds; intertidal to shallow subtidal Family Columbellidae
(in part)

57a Sculpture consisting of closely spaced spiral ridges (in Alia, Columbellidae, these are faint and restricted to the lower half of the body whorl, and are sometimes absent) 58

57b Sculpture consisting of only 1 or 2 prominent ridges on each whorl
(the lower part of the body whorl generally has a number of smaller ridges; in occasional specimens of Nucella emarginata, Nucellidae, which typically has spiral ridges over most of the shell, the ridges may be obscure) Family Nacellidae
(in part)

58a Spiral ridges faint and limited to the lower half of the body whorl (they are most likely to be visible near the columella; use magnification); height up to about 1 cm Family Columbellidae
(in part)

58b Spiral ridges (these may be faint) distributed over all of the larger whorls; height generally greater than 1 cm 59

59a With a sharp tooth on the lower half of the outer lip of the aperture (picture) Nucellidae:
Acanthina spirata

59b Without a sharp tooth on the lower half of the outer lip of the aperture 60

60a Siphonal canal less than one-fourth the total height of the aperture; height generally less than 4 cm; common intertidal species Nucellidae
(in part)

60b Siphonal canal one-fourth to one-third the total height of the aperture (the outer lip of the aperture usually has an angular indentation where the canal begins); height commonly more than 4 cm in most species; strictly subtidal Family Neptuneidae
(in part)

Taxonomic Levels Represented in This Key:

Order Patellogastropoda
Family Batillariidae: Batillaria attramentalis
Family Buccinidae
Family Calyptraeidae
Family Cerithiidae
Family Columbellidae
Family Epitoniidae
Family Fissurellidae
Family Haliotidae
Family Hipponicidae: Hipponix cranioides
Subfamily Lacuninae of Family Littorinidae (formerly Family Lacunidae)
Family Littorinidae
Family Muricidae
Family Naticidae
Family Neptuneidae:
Family Nucellidae
Family Olividae
Family Trochidae
Family Velutinidae
Acanthina spirata
Colus griseus
Fusitron oregonensis
Searlesia dira

Page created by Nathaniel Charbonneau, 7-2002
Edited by: Anna Dyer, Dave Cowles 2005, 2006, 2007, 2008
Hans Helmstetler 12-2002

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Lower taxonomic level	Main Page	Alphabetic Index	Systematic Index	Glossary

1a	Shell permanently cemented to a hard substratum (usually rock), coiled loosely or irregularly and generally twisted, resembling the calcareous tube of a serpulid polychaete more then a snail shell (picture) (picture)	Family Vermetidae
1b	Shell not permanently cemented to a hard substratum, either tightly coiled or tubular, conical, or cap-shaped	2
2a	Shell tubular, conical, or cap-shaped, without obvious coiling	3
2b	Shell obviously coiled, although the spire may be short	9
3a	Shell tubular, slightly curved, the height more then twice the diameter	Family Caecidae
3b	Shell conical or cap-shaped, the height rarely exceeding the greatest diameter (photo)	4
4a	Shell with a dorsal opening at or near the apex (photo) (photo), or with a slight indentation at the anterior margin (such an indentation is present only in the rare and subtidal Arginula bella; it marks the place where a groove on the interior of the shell, beginning at the apex, reaches the margin)	Family Fissurellidae
4b	Shell with neither a dorsal opening at or near the apex nor an indentation on the anterior margin	5
5a	Interior of shell with a shelf (photo) (photo)	Family Calyptraeidae
5b	Interior of shell without a shelf (photo)	6
6a	Apex of the shell usually at or anterior to the middle, sometimes slightly posterior to the middle (if only the shell is available, the open end of the horsehoe-shaped muscle scar faces anteriorly (photo), except in the family Siphonariidae, in which the open end of a nearly C-shaped muscle scar faces the right side [left side, if the shell is observed in ventral view])	7
6b	Apex of the shell decidedly posterior to the middle (at least as far as the beginning of the last quarter) (the foot secretes a calcareous base, and the animal remains attached to this)	Family Hipponicidae: Hipponix cranioides
7a	Outline of the shell, in dorsal view, not symmetrical, the apex slightly to the right of the midline; muscle scar (often indistinct) nearly C-shaped, its open end facing the right side (left side if the shell is observed in ventral view); with a shallow siphonal groove passing through the open end of the muscle scar	Subclass Pulmonata, Family Siphonariidae
7b	Outline of the shell, in dorsal view, symmetrical (unless deformed by an injury) (photo), the apex on the midline; muscle scar horsehoe-shaped, its open end facing anteriorly (photo); without a siphonal groove	8
8a	Interior of shell uniformly whitish, without any color pattern; apex in the anterior third of the shell; exterior with rather conspicuous concentic lamellae (subtidal)	Family Lepetidae
8b	Interior of shell usually with a color pattern of some sort (a blotch in the apical region, marginal markings, etc.) (photo); apex in the anterior or middle third of the shell (in the middle third in Acmaea mitra, the only species in which the interior is uniformly white); concentric lines not often conspicuous	Order Patellogastropoda, Families Acmaeidae, Nacellidae, and Lottiidae
9a	Abalones--shell low and earlike, with a low spire near the posterior end, and with a series of holes (some closed) near the left side; length sometimes exceeding 10 cm (picture)	Family Haliotidae
9b	Shell generally not low and earlike (except in Lamellariidae and Velutinidae), and without a series of holes near the left side; only a few species larger then 10 cm, and nearly all of these have tall spires	10
10a	Shell (completely or almost completely internal in Lamellariidae) with a low profile, thus resembling the shell of a abalone (photo)	11
10b	Shell not resembling that of an abalone	12
11a	Shell thin, translucent white, and completely or almost completely internal	Family Marseniidae
11b	Shell rather firmly calcified, covered by an almost velvety periostracum, and to a large extent external (photo)	Family Velutinidae
12a	Outer lip of the aperture with a deep slit ( the shell, which has a short spire above the proportionately large body whorl, resembles that of a Margarites or Lirularia [Trochidae], its diameter being about equal to its height; found only at depths greater then 400 m)	Family Scissurellidae
12b	Outer lip of the aperture without a deep slit (there may, hovever, be a notch or distinct siphonal canal at the anterior end of the aperture, and there may also be a slight notch on the outer lip near the posterior end of the aperture) (includes most intertidal and subtidal prosobranch gastropods, and some opisthobranchs and pulmonates)	13
13a	Length of the aperture nearly equal to the height of the shell (if there is a spire, it is not raised)	14
13b	Length of the aperture not nearly equal to the height of the shell (there is a raised spire)	15
14a	Shell thick, similar in shape to that of a cowrie, with a series of teeth on the inside of the outer lip of the aperture; aperture not decidedly wider in its anterior half than elsewhere; height about 3 mm	Marginellidae: Granulina margaritula
14b	Shell thin, not resembling that of a cowrie; without teeth on the inside of the outer lip of the aperture; aperture usually widest in its anterior half; height up to nearly 2 cm, but much smaller in some species	Subclass Opisthobranchia, Order Cephalaspidea
15a	Much of the periostracum in the form of conspicuous hairs or bristles	16
15b	Periostracum not in the form of conspicuous hairs or bristles	17
16a	With a prominent siphonal canal that is about 1/3 the total length of the aperture (photo); height up to about 12 cm (or more)	Cymatiidae: Fusitron oregonensis
16b	Without a distinct siphonal canal, but the anterior of the aperture is angled in such a way that it forms a small spout; height generally less than 4 cm	Capulidae (formerly Trichotropidae)
17a	Anterior end of the aperture without a distinct siphonal notch, spout, or canal (photo)	18
17b	Anterior end of the aperture with a distinct siphonal notch, spout, or canal	34
18a	Interior of shell pearly (except in Halistylus pupoideus, family Trochidae); with an operculum (photo)	19
18b	Interior of shell not pearly (it may, however, be colored); with or without an operculum	20
19a	Operculum thin and horny, with numerous spiral lines (photo)	Family Trochidae
19b	Operculum calcified and rather thick, with only a few spiral lines	Family Turbinidae
20a	Diameter of the shell much greater than the height (aperture almost circular, equal to about half the total diameter, which does not exceed 4 mm; without periostracum)	Vitrinellidae: Vitrinella columbiana
20b	Height of the shell equal to or greater than the diameter	21
21a	Columella with 1 or more distinct folds or ridges; height less than 1 cm	22
21b	Columella without any folds or ridges; height may exceed 1 cm	24
22a
22b
23a
23b
24a	Diameter about equal to the height; shell generally almost globose, consisting mostly of the body whorl (umbilicus either conspicuously open or covered by an obvious callus; height of some species attaining 10 cm)	Family Naticidae
24b	Height decidedly greater than the diameter; shell not almost globose, the spire usually at least one-sixth of the total height	25
25a	Height not more than twice the diameter	26
25b	Height considerably more than twice the diameter	30
26a	Umbilicus a slit between the columella and the body whorl (generally on eelgrass or on algae, especially kelps, mid- to low intertidal and subtidal) (formerly Family Lacunidae)	Subfamily Lacuninae of Family Littorinidae
26b	Umbilicus absent or indistinct (in some species, there is a narrow space between the body whorl and the edge of the inner lip of the aperture)	27
27a	Height commonly exceeding 5 mm, and in some species slightly exceeding 1.5 cm; operculum horny; periostracum not uniformly tan or brown (Almagorda subrotundata is brown, but usually has spiral banding) (mostly at higher tide levels on rocly shores, or on rocks, concrete and wood in bays, sometimes in salt marshes)	Family Littorinidae
27b	Height not exceeding 4 mm; operculum horny or calcareous; periostracum sometimes uniformly tan or brown (Assiminea californica, Assimineidae, inhabits salt marshes, but members of the other families to which this couplet leads are typically found at lower levels of rocky or gravelly intertidal areas)	28
28a
28b
29a
29b
30a	Shell highly polished, in some species slightly bent; suturesbetween whorls so slightly indented that they are barely evident (whorls themselves, moreover, are nearly flat); parasitic on echinoderms, and strictly subtidal	Family Eulimidae
30b	Shell not usually highly polished, and not bent; sutures between whorls distinct; not parasitic on echinoderms (but the Epitoniidae are parasitic on various cnidarians)	31
31a	Spire decidedly tapered and generally with more than three whorls; not typically found at higher tide levels in salt marshes	32
31b	Spire scarcely tapered, and generally with only 3 whorls (the older whorls disappear and the uppermost surviving whorl is usually very short and smoothly rounded; typically at highter tide levels in salt marshes	Truncatellidae: Cecina manchurica
32a	Height of the spire shorter than the body whorl; spire usually with 4 or 5 surviving whorls; shell sculpture limited to prominent axial ribs, and when the shell is viewed with the aperture lowermost and facing the observer, the ribs are more nearly parallel to the left side of the shell than to the right side	Rissoinidae: Rissoina newcombiana
32b	Height of the spire considerably greater than the height of the body whorl; spire usually with at least 6 surviving whorls; shell sculpture sometimes limited to axial ribs, but if so, the ribs are more or less parallel to both sides of the shell	33
33a	With both axial ribs and spiral ridges (the intersections of these sometimes form beads), or with spiral ridges only	Family Turritellidae
33b	Sculpture limited to axial ribs (except for a single spiral ridge near the base of the body whorl)	Family Epitoniidae
34a	Upper portion of the outer lip of the aperture with an anal notch If the lip has been fractured, the contours of the growth lines nearest the lip are likely to indicate that an indentation had been present. In species that do not have a distinct anal notch, the following combination of characters may enable one to recognize them as members of this family; width of the aperture less than one half, and usually less than one third, the height of the aperture; prominent axial ribs; foot milky white. Presence of an anal notch, however, is the most reliable feature. In certain species of Antiplanes, the shell is coiled sinestrally rather than dextrally, and this is helpful in assigning them to the Turridae. Most members of the family are subtidal and they typically inhabit soft sediments. None in our region is likely to be found in a rocky intertidal habitat.	53 Turridae
34b	Upper portion on the outer lip of the aperture without an anal notch or trace of a notch	35
35a	Shell highly polished, without any sculpture other then fine growth lines; widest part of the aperture (near its lower end) less then half the diameter of the shell (picture); operculum inconspicuous; typically in sandy substrata	Family Olividae
35b	Shell not polished, and usually with at least some sculpture; widest part of the aperture (generally near its middle) usually at least half the diameter of the shell; operculum usually conspicuous and large enough to close the aperture tightly (picture picture); not necessarily limited to sandy substrata	36
36a	Lowermost portion of the body whorls including the siphonal canal, set off from the rest of it by a conspicuous groove that [may even] interrupt the axial ribs (photo) [though in Nassarius fossatus the axial ribs do not extend this far anteriorly on the body whorl].	Family Nassariidae
36b	Lowermost portion of the body whorl not set off from the rest of it by a conspicuous groove that interrups the axial ribs	37
37a	Shell with at least 8 distinct whorls, not counting 1 or 2 that may have been worn away at the apex (in specimens that have been abruptly worn down to 4 or 5 whorls, one can estimate, on the basis of the surviving portion of the shell, that about 10 whorls have developed; height not exceeding 4 cm	38
37b	Shell with not more than 7 whorls, even if none appears to have been worn away, except in specimens whose hight commonly exceeds 12 cm	41
38a	Siphonal canal half the total height of the aperture; axial ribs prominent, not forming beads where they intersect the faint spiral ridges	Family Neptuneidae: Exiliodea rectirostris
38b	Siphonal canal less than half the total height of the aperture (photo); axial ribs and spiral ridges sometimes forming beads where they intersect	39
39a	Siphonal canal short but obvious; spiral ridges distinctly (and sometimes conspicuously) beaded where intersected by the axial ribs (photo)	40
39b	Siphonal canal barely evident; spiral ridges beaded in some species that have axial ribs, but not in the most common species (Bittium eschrichtii); which lacks axial ribs	Family Cerithiidae
40a	Siphonal canal narrow, directed toward the left at a nearly right angle to the long axis of the shell (as the shell is viewed with aperture lowermost and facing the observer) (photo); with about 12 axial ribs; height up to 3.5 cm; usually in salt marshes	Family Batillariidae: Batillaria attramentaria
40b	Siphonal canal broad, directed to the left at about a 45 degree angle from the long axis of the shell; with at least 12 axial ribs (and sometimes more than 30); height not often exceeding 1 cm	Cerithiopsidae
41a	Shell either with axial ribs as well as spiral ridges, or with only spiral ridges	42
41b	Shell with only axial ribs	Family Volutidae
42a	Shell sculpture limited to spiral ridges	55
42b	Shell with axial ribs (these may be low and incospicuous, however) or thin axial lamellae (picture), as well as with spiral ridges	43
43a	Axial ribs limited to the spire (the body whorl may have a few irregularly spaced grooves that are perpendicular to the spiral ridges, and young specimans of Searlesia dira, under 2 cm long, have axial ribs on the body whorl) (photo)	44
43b	Axial ribs or lamellae extending to the body whorl, even though they may be less distinct on the body whorl than on the spire	45
44a	Columella with 2-5 folds; periostracum light brown; spiral ridges faintly evident on the inside of the outer lip of the aperture; subtidal	Family Cancellariidae: Neoadmete modesta
44b	Columella without folds; periostracum gray; dark lines in the furrows between spiral ridges of the body whorl visible on the inside of the aperture; intertidal and subtidal	Family Buccinidae: Searlesia dira
45a	Axial ribs on the body whorl restricted to the upper half of it (if continued into the lower half of the body whorl, they become much less prominent) (photo)	46
45b	Axial ribs distinct on at least much of the lower half of the body whorl, and as prominent as those on the upper half of the body whorl	49
46a	With a series of folds on the inside of the outer lip of the aperture as well as on the columella	Family Columbellidae (in part)
46b	Folds sometimes present either on the inside of the outer lip of the aperture or on the columella, but not on both	47
47a	With folds on the inside of the outer lip of the aperture (these coincide with spiral ridges on the outside of the body whorl); without folds on the columella	Family Fusinidae
47b	Without folds on the inside of the outer lip of the aperture; with or without folds on the columella	48
48a	Axial ribs rather sharp; with 2-5 (usually 2 or 3) folds on the columella	Family Cancellariidae: Admete gracilior
48b	Axial ribs low and broad; without folds on the columella	Family Neptuneidae: Plicifusus griseus (now Family Buccinidae, Colus griseus)
49a	Siphonal canal (measured from the angle in the outer lip of the aperture where the canal begins) one-third to one-half the total height of the aperture	50
49b	Siponal canal decidedly less than one-third the total height of the aperture (picture)	51
50a	Either with axial ribs and spiral ridges equally well developed and prominent, or axial ribs represented by thin lamellae and spiral ridges faint	Family Muricidae
50b	Axial ribs poorly developed in comparison with the prominent spiral ridges	Family Neptuneidae
51a	Axial sculpture consisting of thin, frillylamellae (photo); spiral sculpture, which may be obscured by the lamellae, consisting of 1 or 2 prominent ridges on each whorl (picture)	Nucellidae: Nucella lamellosa
51b	Axial sculpture consisting either of fairly broad ribs or of wrinkles (these may be irregular and discontinuous), but not of frilly lamellae; spiral sculpture consisting of closely spaced spiral ridges	52
52a	With 2 or 3 folds on the columella	Cancellariidae: Cancellaria crawfordiana
52b	Either with 1 fold or none on the columella	53
53a	Without a fold on the columella; periostracum, if persistent, straw-colored or dark brown	Family Neptuneidae (in part)
53b	With 1 fold on the columella; periostracum blackish or whitish	54
54a	Periostracum blackish, thick, cracked, but otherwise more or less continuous except where the spire is eroded; inside of aperture purplish brown; axial ribs and spiral ridges about the same size; height up to about 2.5 cm; intertidal, in mudflats	Nassariidae: Ilyanassa obsoleta
54b	Periostracum whitish or dull brown; inside of aperture white or pinkish; axial ribs much more pronounced than the spiral ridges; height up to 7 cm; subtidal	Family Buccinidae: Buccinum spp
55a	Columella with 2 or more folds	56
55b	Columella without folds	57
56a	Spiral ridges present over the entire shell; columella with about 5 folds; restricted to deep water	Family Volutomitridae
56b	Spiral ridges present only on the lowest part of the body whorl, near the siphonal canal; columella with 2 or 3 folds; intertidal to shallow subtidal	Family Columbellidae (in part)
57a	Sculpture consisting of closely spaced spiral ridges (in Alia, Columbellidae, these are faint and restricted to the lower half of the body whorl, and are sometimes absent)	58
57b	Sculpture consisting of only 1 or 2 prominent ridges on each whorl (the lower part of the body whorl generally has a number of smaller ridges; in occasional specimens of Nucella emarginata, Nucellidae, which typically has spiral ridges over most of the shell, the ridges may be obscure)	Family Nacellidae (in part)
58a	Spiral ridges faint and limited to the lower half of the body whorl (they are most likely to be visible near the columella; use magnification); height up to about 1 cm	Family Columbellidae (in part)
58b	Spiral ridges (these may be faint) distributed over all of the larger whorls; height generally greater than 1 cm	59
59a	With a sharp tooth on the lower half of the outer lip of the aperture (picture)	Nucellidae: Acanthina spirata
59b	Without a sharp tooth on the lower half of the outer lip of the aperture	60
60a	Siphonal canal less than one-fourth the total height of the aperture; height generally less than 4 cm; common intertidal species	Nucellidae (in part)
60b	Siphonal canal one-fourth to one-third the total height of the aperture (the outer lip of the aperture usually has an angular indentation where the canal begins); height commonly more than 4 cm in most species; strictly subtidal	Family Neptuneidae (in part)