Channeled Nassa Shell, Caesia fossata

Channeled Nassa Shell, Caesia fossata. Shell collected near shore, San Diego, California, May 2007. Size: 3.8 cm (1.5 inches) x 2.4 cm (0.9 inches). Collection, photograph and identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny: The Channeled Nassa, Caesia fossata (Gould, 1850), is a gastropod mollusk that is a member of the Nassariidae Family of Mud Shells. The genus Caesia is one of forty-seven genera in this family, and there are four species in this genus. They are also known as the Channeled Basket Welk, the Channeled Dog Whelk, and the Giant Western Nassa and in Mexico as Nassa Canalizada.

Description: Channeled Nassa shells have a large body whorl and a high spire. They have strong diagonal ridges that run the length of the shell, but are more obvious on the top half of the shell. They also have numerous, fine, spiral lines that cross these ridges, giving a basket-weave appearance. Their siphon canal is short, and curved. The aperture is oval in shape, and has low ridges on the inside of both lips. The anterior end of the body whorl is separated from the rest of the body whorl by a deep channel. The exterior of the shell is an orange-tan color and the aperture lips are brighter orange. The interior is white. Channeled Nassa Shells reach a maximum of 3.2 cm (1.2 inches)  in length.

Habitat and Distribution: Channeled Nassa Shells are found on sand and mudflats in the intertidal zone, and to depths up to 18 m (60 feet). They favor areas with limited water movement. Channeled Nassa Shells are a temperate Eastern Pacific species. In Mexican waters they have a limited range. They are found along the west coast of the Baja Peninsula, from the northern border to San Ignacio Lagoon, Baja California Sur. They have not been documented from the Sea of Cortez.

Ecology and Behavior:  Channeled Nassa Shells are scavengers that feed primarily on carrion and decaying organic matter. They are prey for fish, crabs, and shore birds. Channeled Nassa Shells  are gonochoric and reproduce sexually.  From a conservation perspective they have not been formally evaluated however they are common with a relatively wide distribution and should be consider to be of Least Concern.

Synonyms: Buccinum elegans, Buccinum fossatum, Nassa moreti, Nassa reevei, and Nassarius fossatus.