CONCHOLOGY. 37 



2. Genus Gastrochsena. PI. VI. 

 Animal. Unknown. 



Shell. Equivalve, somewhat cuneiform with a very large oval 

 and oblique aperture anteriorly ; posterior extremity nearly closed ; 

 hinge linear ; marginal and without teeth. Three species. 

 Gastrochsena cuneiformis. Gastrochaena mytiloides. 

 G. modiolina. 



FAMILY III. 



SoLEjfiDA. Four genera. 



1. Genus Solen. PI. VI. 



Animal. Body cylindroid, much elongated; the mantle m 



form of a canal open at both ends, closed in the rest of its extent 



by a thick epidermis which surrounds it ; a cylindroid anterior 



foot. 



Shell. Equivalve, extremely inequilateral, the summits very 

 small, and entirely at the commencement of the dorsal line ; one 

 or two teeth in the hinge. Inhabits the seas of America and Eu- 

 rope. Nineteen species, 



Solen vaginus. Solen vaginoides. 



S. corneus. S. siliqua. 



S. ensis. S. cultellus. 



S. pygmaeus. S. planus. 



S. ambiguus. S. minutus. 



S. dombeii. S. constrictus. 



S. javanicus. S. coarctatus. 



S. caribaeus. S. rostratus. 



S. antiquatus. S. violaceus. 



S. giganteus. 



2. Genus Panopsea. PI. VI. 

 Animal. Unknown. 



Shell. Regular oval, elongated, gaping at both ends, equivalve, 

 inequilateral ; summit little marked and anterodorsal ; hinge com- 

 plete ; similen formed by a conical primary tooth, before a short, 

 compressed, ascending callosity, ligament exterior, attached to the 

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