173 



P. tarentina, 

 ' punctata, 

 ' puncturata, 

 ' Javanica, 



P. tuberculifera, 

 ' miniata, 

 ' viridula, 



P. pectinata, 

 ' galathea, 

 ' pellucida, 



P. tricostata, 

 ' australis, 

 ' cymbularia. 



SEMI-PHYLLIDIANA.— Two Genera. 



Pleurobranchus. Shell internal, dorsal, thin, flattened, often oblique 

 oval. 



P. Peronii, 



P. Laqueare. 



Umbrella. Shell external, orbicular, subirregular, nearly flat, slightly 

 convex above, white, with apex near the middle; margin acute, internal sur- 

 face rather concave; having a callous disc, colored, depressed in the centre, 

 surrounded by a smooth border. 



U. Indica, U. Mediterranea. 



CALYPTRACIANA.— Seven Genera. 



Shell always external, covering the animal. 



Parmophorus. Shell oblong, subparallelopipedal, slightly convex above, 

 obtuse at the extremities, anteriorly channelled by a slight sinus, and having 

 towards the posterior part a small, pointed apex, inclined backwards; the 

 lower surface slightly concave. 



P. australis, P. granulata. P. ambigua, 1 fossil species. 



' brevicula, 



Em arg inula. Shell shield-like, conical; summit inclined; the cavity 

 simple, having a notch or hollow cut on its posterior margin. 



E. fissura, E. rubra, E. crystallina, 3 fossil species. 



Fissurella. Shell shield-like or depressed conical, concave below, per- 

 forated at the summit; without any spire; the perforation oval or oblong. 



Pileopsis. Shell univalve, obliquely conical, anteriorly recurved; apex 

 bent, almost spiral; aperture rounded, elliptical; the anterior margin shortest, 



