PLEUROBRANCHUS. UMBRELLA. PARMOPHORUS. 7 



summit blunt^ and inclined toward the front ; 

 margin strongly digitated, and within of a tor- 

 toise-shell brown ; muscular impression tawny. 

 2... if. W. 37. 16. 



LES SEMI-PHYLLIDIENS. 



PLEUROBRANCHUS. 



Shell internal, fragile, dorsal, flattened, and ob- 

 liquely oval. 



P. MEMBRANACEUS. S. 232. 

 UMBRELLA. 



Shell external, orbicular, slightly irregular, flat- 

 tish, rather convex above, with a small sub- 

 central apex ; margin sharp ; interior slightly 

 concave, and offering a coloured callous disc ; 

 lips smooth. 

 U. iNDiCA. S. 233. 



LES CALYPTRACIENS. 



PARMOPHORUS. 



Oblong, someiohat in the form of a parallelopiped ; 

 slightly convex above, with a small sinus above ; 

 apex pointed and inclined backivards. 

 P. AUSTRALis. Solid, smooth, but appears 



