COMPARISON OF TWO “CLASSIC” CASSID GASTROPOD SPECIES

Cassid gastropods are memorable for their medium-sized, sturdy, and pretty shells. As shown below, some of them can have a detailed carved image (i.e., cameo) on the back of their shell, and some of cameos are expensive collector's items.

The shell terms length and width, which are used herein, were defined by Groves and Squires, 2023. Length = greatest distance between anterior and posterior termini. Width = greatest distance between lateral margins.

Phylum Mollusca 

Class Gastropoda

Order Littorinimorpha

Family Cassidae

Genus Cypraecassis

     This genus has a geologic range from the Miocene to present day.

Two views (front and back) of Cypraecassis rufa, length 3 inches [= 7.25 cm], width 1 ¾ inches [= 4.7 cm], from southern Africa. This specimen has, most likely, some bleaching of its shell's color by sunlight before being collected.

A cameo (hand carving) on the back of a specimen of Cypraecassis rufa.  Intricate cameos were most commonly made before the 1900's.

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Two views (front and back) of Cypraecassis testiculus, length 4 inches [= 9.75 cm], width 2.5 inches [= 6.5 cm], locality unknown but undoubtedly from tropical shallow-marine water. Although this species is similar to the previous species, C. rufa shown above, there are important differences other than size and coloration (study the illustrations presented here, and you will soon detect these differences. Just a few examples of these are the following: lack of spiral bands on the top of C. testiculus, fewer and coarser “ribs” on the aperture (opening to the interior) of C. testiculus, and so on. The more you carefully compare the two shells, the more differences you will find---welcome to the fascinating world of identification of mollusk shells and how species differ in subtle but important ways.

REFERENCES:

https://www.sealifebase.se/summary/Cypraecassis-rufa.html  

Groves, L.T. and R.L. Squires. 2023. Revision of northeast Pacific Paleogene cypraeoidean gastropods including recognition of three new species: implications for paleobiogeographic and distribution for faunal turnover. PaleoBios 40(10):1–52. (pdf free and very easy to acquire).