DESCRIPTION. 179 



Linnaean genus. Nor will the extension of the 

 membrane over the whole surface exclude it ; for 

 a regular gradation through the next species and 

 C. iunicatus may be traced from this to any indi- 

 viduals of the genus which are perfectly uncovered. 



The specimen figured in the plate and the fol- 

 lowing one are both deposited in the British Mu- 

 seum, They have been examined by Dr. Blain- 

 ville of Paris, by whom a communication respect- 

 ing them has, it is understood, been made to the 

 French Philomatique Society. The names he has 

 affixed to the two species are Cryptoconchus po- 

 rosus, and C. larvceformis. 



To the politeness of Dr. Leach, of the British 

 Museum, the author owes his opportunity of ma- 

 king the annexed drawings, and of inspecting the 

 mollusca. 



Fig. 2. 3. 4. C, larvceformis. 



Shell S-valved, valves without any keel, dissi- 

 milar, covered partially with the membrane. 



Specimens having the three posterior valves 



white and smooth, bluish flesh-coloured at the 



sides, the others brown and striated ; coriaceous 



membrane rough, cinereous olive, with a few scat- 



n2 



