Poulson’s Rock Shell, Roperia poulsoni

Poulson’s Rock Shell, Roperia poulsoni. Size: 5.8 cm (2.3 inches) x 3.0 cm (1.2 inches). Shell collected off the beach of Bahía Concepción, Baja California Sur, October 2019. Collection, photograph and identification courtesy of Bob Hillis, Ivins, Utah.

Poulson’s Rock, Roperia poulsoni (Carpenter, 1864), is a member of the Muricidae Family of Rocks, that is also known as Poulson’s Dwarf Triton. The shell is spindle shaped that consists of six whorls that become increasingly convex as the descend, a high spire, nine varices and spiral ridges with a cross pattern gives the entire exterior a knobby texture and an open siphon canal. The aperture is about half as long as the entire shell with a scalloped outer lip the inside of which has three to four small “teeth” (dentions). The exterior of the shell is gray in color, with white and brown spiral lines; the interior is shiny white. Poulson’s Rock Shells reach a maximum of 6.5 cm (2.6 inches) in length and 3.4 cm (1.3 inches) in height.

Poulson’s Rock Shells are found on rocks in the intertidal zone to depths up to 4 m (15 feet). They are found along the northwest and central coasts of the Baja south to Magdalena Bay, Baja California Sur.

Synonyms include Fusus roperi and Oceanebra poulsoni.