188 THE BERMUDA ISLANDS. 



more than one-third the width of base, yellowish-green ; mouth 

 margin papillose, bunchy; under surface obscurely or obso- 

 letely tuberculose; dorsal surface closely verrucose, with finer 

 granules interspersed between the warts. 



Anal aperture immediately beyond the extremity of foot, 

 infra-marginal to a raised border; respiratory orifice between 

 the anal pore and the apex of body. 



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- 

 Paoific waters, although one species is known from Arctic 

 America, one from the California coast, and one from the west 

 coast of South America (Bergh, in Semper's Reisen im Archipd 

 d. Philippinen, Land Mollusks, VI). 



The Bermudian species appears to be most nearly related to 

 0. Carpenteri, from the California 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 agree- 

 ing with the determinations made by Bergh for manifestly 

 the same species. 



Emarginula dentigera. PI. 17, fig. 7. 



Shell flattened, scutiform, broadened posteriorly, and with 

 the apex slightly sub-central ; surface with radiating ribs, 

 which alternate in size sometimes two smaller ones between 

 each pair of larger ribs and project (the larger ones) prom- 

 inently beyond the general margin. The impressed concentric 

 lines give to the ribs a knobbed appearance. Fissure fairly 

 long, narrow. 



Length nearly .25 inch. ; height .1 inch. 



