Taken primarily from Kozloff, 1987, 1996 p. 226 (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 | Spiral ridges and grooves limited to the lower portion of the body whorl | 2 |
| 1b | Spiral ridges and grooves not limited to the lower portion of the body whorl | 5 |
| 2a | ||
| 2b | ||
| 3a | ||
| 3b | ||
| 4a | ||
| 4b | ||
| 5a | Axial ridges obviously not parallel to the long axis of the shell (they are directed slightly to the left as they extend downward); height rarely attaining 1.5 cm (often with distinctive light and dark markings unless the shell is covered with foreign material | Amphissa versicolor |
| 5b | Most axial ridges almost parallel to the long axis of the shell | 6 |
| 6a | Middle third of the outer lip of the aperture (in mature specimens, at least 2 cm high) parallel to the long axis of the shell (photo); height to 3 cm; common intertidal and subtidal species | Amphissa columbiana |
| 6b | Middle third of the outer lip of the aperture (in mature specimens, at least 1 cm high) curved; height to 1.5 cm; subtidal, rare | Amphissa reticulata |