Cranopsis cucullata (Gould, 1846)

Common name(s):   Hood puncturella, Hooded puncturella, Helmet puncturella
Synonyms: Puncturella cucullata Puncturella cucullata
Class Gastropoda
Order Archaegastropoda
Suborder Pleurotomariina
Cranopsis cucullata collected from a red octopus (Octopus rubescens) midden.  Length  1 cm.
(Photo by: Dave Cowles March 2008)
Description:   As with other members of this family, the shell is cap-shaped and has a dorsal opening near the apex or a slight indentation at the anterior margin.  Craniopsis cucullata has a narrow slit just anterior to the apex of the shell and a seam running from this slit down to the anterior margin of the shell (photo).  The large, sharp primary and small secondary ribs are of very different size and the margin is dentate where the large primary ribs reach it.  There are 13-23 (usually about 16) primary ribs, each separated by about 3-4 faint secondary ribs.  The primary ribs project as much as 2-3 mm from the margin.  The apex may curve anteriorly.  White inside and out.  Length to 4 cm.

How to Distinguish from Similar Species: Puncturella. multistriata has about 30 primary ribs, each separated by 1-3 secondary ribs.  The primary ribs do not project more than 1 mm beyond the shell margin. Puncturella galeata has no anterior seam, about 49-63 ribs, and only grows to 2 cm.  Other keyhole limpets such as Diodora aspera and Fissurellidea bimaculata have a round opening at the apex instead of a slit in front.

Geographical Range:  Alaska to Cabo San Qintin, Baja California

Depth Range:  Low intertidal to 200 m; more common subtidally

Habitat:  On and under rocks

Biology/Natural History:

Cranopsis was formerly considered to be a subset of Puncturella.


 
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References:

Dichotomous Keys:
  Flora and Fairbanks, 1967 (as P. cucullata)
  Kozloff 1987, 1996
 

General References:
  American Fisheries Society, 1998
  Harbo, 1997
  Morris, 1966 (as P. cucullata)
  Sept, 1999

Scientific Articles:

Web sites:

General Notes and Observations:  Locations, abundances, unusual behaviors:

3d

This closeup shows the anterior slit and the seam which leads from the slit to the anterior edge of the shell.  This photo was made from a stack of photos which were combined by a computer algorithm to create a much greater depth of field (photo by Dave Cowles, technology by Keyence DHX-100 digital microscope and software)


Underside
The anterior slit is separated from the actual apex of the shell by a partition, as can be seen in this view of the underside.


Authors and Editors of Page:
Dave Cowles (2008):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)