CONCHIFERA OR BIVALVES. 67 



Solen, unequally gaping at the sides ; one coni- 

 cal tooth in each valve, with a thick callosity 

 on the side; ligament external; pallial impres- 

 sion deep. Animal unknown. — 4 species re- 

 cent, 2 of which are also fossil. 



This is a large and handsome shell, but it is 

 not often met with in collections in a perfect 

 state, the valves seldom being found together 

 after the death of the animal : the locality of 

 the genus is the Mediterranean and New Hol- 

 land. 



17. Glycimeris. — Shell transverse, possess- 

 ing no teeth, but thick 

 projecting callosities, 

 and gaping at both ends ; 

 ligament external, placed 

 on the short side of the 

 valves ; bosses generally eroded. Animal, foot 

 small and cylindrical, projecting from one side, 

 and two united tubes, which cannot enter the 

 shell, issuing from the other. — 2 species recent, 

 and 1 fossil. 



Found in the northern seas, on sands. It is 

 covered with a thick, black, horny epidermis, 

 passing over the edge of each valve. 



f 2 



