328 PROCEEDINGS OF THE ACADEMY OF [1888. 



Length about three-quarters of an inch. 



About a dozen specimens, found in a rock hollow on the north 

 shore just beyond Wistowe, near Flatts Village, at an elevation 

 of about two feet above the water. 



This is, as far as I am aware, the only species of Onchidium that 

 has thus far been recorded from the western Atlantic. Its occurrence 

 is, therefore, of considerable interest as bearing upon the subject of 

 geographical distribution. Nearly all the species of the genus are 

 confined to the Eurafrican and Indo-Pacific waters, although one 

 species is known from Arctic America, one from the Californian 

 coast, and one from the west coast of South America (Bergh, 

 in Semper's Reisen im Archipel d. Philipjiinen, Land Mollusks, 



VI). 



The Bermudian species appear to be most nearly related to 

 0. Carpenteri, from the Californian coast, but differs from it in color. 

 The positions of the anal and respiratory apertures differ from what 

 is indicated by Stearns (Proc. Acad. Nat. Sci., Phila., 1878) to 

 exist in the west American form, although agreeing with the deter- 

 minations made by Bergh for manifestly the same species. 



