﻿144. 



Acasta. Shell sessile, oval, subcorneal, composed of separable pieces; 

 cone formed of six unequal, lateral valves, united together; the base a lamina 

 or orbicular valve, concave on the inside, resembling a patella or little cup. 

 Operculum quadrivalve. 



A. montaguii, A. glans, A. sulcata, A. tubulosa. 



Creusia. Shell sessile, fixed, orbicular, convex, conical, quadrivalve; 

 valves unequal, united together, sutures distinct. Operculum internal, quad- 

 rivalve. 



C. stromia, C. spinulosa, C. verruca. 



Pyrgoma. Shell sessile, univalve, rather globular, ventricose, convex 

 above, apex perforated; aperture small, elliptical. Operculum quadrivalve. 



P. canccllata. 



ORDER II. PEDUNCULATED CIRRPHIPEDA. 



The body is supported by a moveable, tubular pedicle, having the base 

 fixed on marine substances. This order consists of two divisions, viz. 

 I. The shell composed of contiguous pieces. II. The shell composed of 

 distant pieces. 



DIVISION I. Shell composed of contiguous jneces. — Two Genera. 



Anatifera. Shell compressed at the sides, composed of five valves, 

 which are contiguous and unequal; the lower side valves the greatest. 



A. lffivis, A. dentata, A. vitrea, A. aculeata. 



' villosa, ' striata, 



Pollicipes. Shell compressed at the sides, multivalve, valves rather con- 

 tiguous, unequal; in number, thirteen or more; the lower side valves the smallest. 



P. cornucopia, P. scalpellum, P. pcronii, P. homii. 



' mitella, 



DIVISION II. Shell composed of distant pieces. — Two Genera. 



Cineras. Shell composed of five testaceous, oblong valves, separate, not 

 covering the whole of the body; two at the sides of the aperture, the others 

 on the back. 



('. vittata. 



