CRUCIBULUM: AN INTERESTING SEA SNAIL

This post concerns two species found today in the tropical waters of the west coast of the Americas. They belong to Crucibulum Schumacher, 1817, a genus of sea snails (gastropods) that resembles some tide-pool limpets, but is not one. By the way, Crucibulum is also a genus of fungi (found in birds’ nests), but this usage does not conflict with Schumacher’s name because snails are classified in Kingdom Animalia.

Two species of Crucibulum are illustrated below. The first is Crucibulum umbrella (Deshayes, 1830), from the state of Jalisco, which fringes the Pacific Ocean in western Mexico. This species lives on wave-swept rocks at low tide. Three views are shown:

Dorsal, side, and ventral. Notice the conical internal “cup.” At its apex, it is attached to its shell, but this “cup” is otherwise free along its margin. Note: This specimen of C. umbrella is usually large. Most specimens of this species are less than 60 mm wide, but this specimen has a maximum diameter of 87 mm and is 23 mm tall (probably a world’s record for this species). 

The second species is Crucibulum scutellum (Wood, 1828) from Baja California (exact locality not know, but this species lives from Cedros Island, Baja California to Ecuador. This species lives on other shells on intertidal mudflats to offshore depths of 27 m. Three view are shown: dorsal, side, and ventral. Notice that the conical internal “cup,” which is  attached at its apex is also attached via a narrow, curving ridge (indicated by the red arrow). The illustrated specimen is 55 mm wide, 30 mm tall, and 75 mm in length.

   

At first glance, genus Crucibulum, the snail, resembles a limpet gastropod, but Crucibulum belongs to a wholly different group of gastropods. Crucibulum belongs to family Calyptraeidae, commonly referred to the “cup-and-saucer” sea snails. Fossils of this family have a geologic record extending back to the Cretaceous, and the geographic distribution of this family (with its lowly moderate number of genera) is widespread.