MARINE MOLLUSCA OP THE UNITED STATES 99 



6. C. EMERSONII, Conthouy. Fig. 203. 



Am. Journ. Sci., xxxiv. 217. 1838. 

 Chiton vestitus, Sowerby, Zool. Journ., iv. 368. 



Shelf ovate-oblong, broadest behind ; valves uniform, each 

 with a central heart-shaped area, with bead-like granules or tuber- 

 cles in concentric. series round the margin, the remainder covered 

 with a soiled downy membrane ; marginal membrane with series 

 of yellow hairy tufts ; whitish. 



Length 20, width 12.5 mill. 



^ New England. 



7. C. RUBER, Lowe. Fig. 204. 



Zool. Journ., iii. 101, t. 5, f. 2. 



Shell small, oval, elevated, carinated ; surface smooth under 

 the lens, except the lines of growth ; valves strongly beaked ; 

 light bright red or flesh-color under a blackish pigment ; interior 

 bright rose-red. 



New England. (Eur.) 



Distinguished from C. marmoreus by its unpunctured surface. 



ORDER III. OPISTHOBRANCHIATA. 



SECTION A. TECTIBRANCHIATA. Animal usually provided with 

 a shell, both in the larval and adult state; branchiae covered by 

 the shell or mantle ; sexes united. 



SECTION B 4 . NUDIBRANCHIATA. Animal destitute of a shell ex- 

 cept in the embryo state; branchiae always external, on the back 

 or sides of the body ; sexes united. 



SECTION A. 



Family TORNATELLID^E. Shell external, solid, spiral or convo- 

 luted ; subcylindrical ; aperture long and narrow; coluraella 

 plaited ; sometimes operculated. 



Family BULLION. Shell invested by the animal, globular or 

 cylindrical, convoluted, thin, often punctate striated ; spire small 

 or concealed; aperture long, rounded, and sinuated in front; lip 

 sharp. No operculum. 



Family TORNATELLID^E. 



Genus TOBNATELLA, Lamarck. 



Extr. d'un Cours. 1812. 



Shell solid, ovate, with a conical, many-whorled spire ; spirally 

 grooved or punctate striate ; aperture long, narrow, rounded in 



