The tropical shallow-marine gastropod genus Casmaria (family Cassidae = the "helmet shells") is widely distributed on sandy bottoms in the Indo-Pacific region: from Madagasgar to Hawaii and some Caribbean Sea localities. The word Casmaria is Latin for “a helmet shape from the sea.”
Only a few living species of Casmaria species have been identified. The two most commonly occurring ones are C. erinaceus (Linnaeus, 1758) and C. ponderosa (Gmelin, 1791). Both are very widespread. They show morphologic variation, thus they have been commonly referred to as polymorphic species. A molecular/gene study by Fedosov et al. (2014) showed that C. erinaceus, characterized by relatively thin shells with considerable ornamentation and coloration, is the same species as C. ponderosa, characterized by thick sturdy shells with reduced ornamentation and coloration.
I recently came across a small-sized specimen (shown below) of Casmaria with solid/heavy, robust shells having sparse but prominent ornamentation of ribs and nodes, as well as having limited coloration. I tried unsuccessfully to identify this specimens as to species, based only on shell morphology. Although it resembles C. ponderosa it is not a perfect match. After reading the paper by Fedosov et al., I would identify this specimen as part of the C. erinaceus “species complex
Three views (ventral, right side, and dorsal) of Casmaria ponderosa? with an almost monochromic (white), heavy, thick shell: length 3.5 cm, width 2.1 cm. Australia.
Reference Cited:
Fedosov, A. et al., 2014. A new species of Casmaria H. Adams & A. Adams, 1853 (Gastropoda, Cassidae) from the Philippines identified by molecular data. European Journal 78:1–13. [a pdf is available and free].
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