8 GENERA OF SHELLS. 



nate, with distinct sutures. Operculum inte- 

 rior, bivalve. 



C. stomia, spinulosa, verruca. 



Pyrgoma. Shell sessile, univalve, globose, 

 ventricose, convex above, perforated at summit, 

 aperture small, elliptical. Operculum bivalve; 



P. cancellata. 



Order II.— PEDUNCULATED CIRRHIPEDA. 



Body supported hy a coriaceous, movable, tubular pedun- 

 cle, the base of which is fixed to marine substances. 

 Shell composed of cçntiguous pieces. 



Anatifera. Shell compressed at sides, five 

 valved ; valves contiguous, unequal, lower one 

 of the side valves largest. 



A. laevis, villosa, dentata, striata, vitrea. 



PoLLiciPES. Shell compressed at sides, 

 multivalve ; valves nearly contiguous, unequal, 

 thirteen or more, lower one of the side valves 

 smallest. 



P. cornucopiae, mitella, scalpellum, villosus. 

 Shell composed of distant pieces^. 



CiNERAs. Shell af five oblong, separate 

 valves, not covering the body entirely, two at 

 the aperture, the others dorsal. 



C. vittata. 



Otion. Shell of two small, semilunar, sepa- 

 rate, testaceous valves, adhering laterally near 

 the aperture. 



O. Cuvieri, Blainvillii.. 



