Serrated Cup-and-Saucer Shell, Crucibulum serratum

Serrated Cup-and-Saucer Shell, Crucibulum serratum. Shell collected off the beach of Punta Chivato, Baja California Sur, May 2025. Size: 1.7 cm (0.7 inches) x 0.3 cm (0.1 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Serrated Cup-and-Saucer Shell, Crucibulum serratum. Shell collected off the beach of Punta Chivato, Baja California Sur, May 2025. Size: 2.0 cm (0.8 inches) x 0.7 cm (0.3 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Phylogeny: The Serrated Cup-and-Saucer Shell, Crucibulum serratum (Broderip, 1834), is a gastropod mollusk of the Calyptraeidae Family of Cup-and-Saucer and Slipper Shells. The Crucibulum Genus is one of eleven genera in the Calyptraeidae Family, and there are nineteen species in the Crucibulum Genus. The name Crucibulum comes from New Latin and refers to the crucible-shaped or pot-shaped structure of these shells. Serratum is Latin for “serrated” or “saw-toothed”.

Description: Serrated Cup-and-Saucer Shells  are generally ovate in outline. They vary in profile from fairly flattened to being as high as they are long.  The apex is forward of the center. Strong radial folds extend to the margins, forming a serrated edge.  The inside cup is flattened against the outside shell. These shells are white, often with a radiating chestnut colored band. Serrated Cup-and-Saucer Shells reach a maximum of 2.0 cm (0.8 inches) in length.

Habitat and Distribution: Serrated Cup-and-Saucer Shells are a poorly documented species and sources vary in the information regarding their distribution and lifestyle. They are found attached to rocks, and possibly, other shells, especially gastropods. They live in the intertidal zone, and to an unknown depth. They are a subtropical to tropical Eastern Pacific species. Serrated Cup-and-Saucer Shells are found in all Mexican waters of the Pacific Ocean with the exception that they are absent from north of San Carlos Bay, Sonora in the Sea of Cortez and from the  west coast of the Baja Peninsula.

Ecology and Behavior: Serrated Cup-and-Saucer Shells are suspension feeders that feed primarily on plankton, which they capture with mucus nets created by their gills. It is thought that they are prey for crabs, fish, and gastropods. They are gonochoric and reproduce sexually, through broadcast spawning. Their engagement in any type of commensal, parasitic, or symbiotic relationship has not been formally documented. From a conservation perspective the Serrated Cup-and-Saucer Shell has not been formally evaluated.

 Synonyms: Calyptraea serrata.