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. 
Bese lgs) W. 3/7. 16. 
LES SEMI-PHYLLIDIENS. 
PLEUROBRANCHUS. 
Shell internal, fragile, dorsal, flattened, and o6- 
liquely oval. 
P. MEMBRANACEUS. S. 232. 
UMBRELLA. 
Shell external, orbicular, slightly irregular, fiat- 
tish, rather convex above, with a small sub- 
central apex; margin sharp ; interior slightly 
concave, and offering a coloured callous disc ; 
lips smooth. 
U. inpica. S. 233. 
LES CALYPTRACIENS. 
PARMOPHORUS. 
Oblong, somewhat in the form of a parallelopiped ; 
slightly convex above, with a small sinus above ; 
apex pointed and inclined backwards. 
P. austRALis. Solid, smooth, but appears 
