Sclerodoris tanya (Marcus, 1971)
Mrs. Eveline Marcus liked cats; she would often paste cut- outs of cat silhouettes on her correspondence. So it is only appropriate that she named probably the only species of nudibranch with a cat patronym! This species was originally described in the genus Doris, based on one specimen collected from Newport Bay, California. In the same paper Chromodoris sphoni (in the genus Felimida) was also named, which is even more appropriate, because Tanya was the name of Gale Sphon's cat. I met her once, but not being a cat person, I was not really impressed....I was impressed when I met Mrs. Marcus.
To the nudibranch. It is the only eastern Pacific species of Sclerodoris; that genus is mainly in the Indo-Pacific region, from Hawaii to Africa and Japan. Many years ago I published an article in The Veliger rectifying its generic placement, commenting on its range, publishing SEMs of the radula and discussing its distribution. It is basically a southern California to Gulf of California endemic, reported from various locations in southern California, along the Pacific coast of Baja California, and inside the Gulf of California (including Puerto Peñasco, San Felipe, Bahía de los Angeles, and Isla San José)
When you turn over a rock and see this species, you think for a moment it is just another dirty gray and black mottled sponge. It has a highly rugose notum, with deep pits and irregular tubercles. The dorsum is rather three-sided, flat in the middle. I have not yet seen it on a prey sponge.
It ranges in length up to about 50 mm (around 2 inches).
Marcus, Eveline du Bois-Reymond. 1971. On some euthyneuran gastropods from the Indian and Pacific Oceans. Proc. Malac. Soc. London 39 (5): 355-369.