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. P^DUNCULATED CIRRHIPEDA. 



Body supported by a coriaceous, movable, tubular pedun- 

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

 Shell composed of contiguous pieces. 



ANATIFERA. Shell compressed at sides, five 

 valved ; valves contiguous, unequal, lower one 

 of the side valves largest. 



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



POLL.ICIPES. Shell compressed at sides, 

 multivalve ; valves nearly contiguous, unequal, 

 thirteen or more, lower one of the side valves 

 smallest. 



P. cornucopia?, mitella, scalpellurn, villosus. 

 Shell composed of distant pieces. 



CINERAS. Shell of 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. 



