38 ~ CONCHOLOGY. 
and oblique aperture anteriorly ; posterior extremity nearly closed ; 
hinge linear ; marginal and without teeth. Three species. 
Gastrochena cuneiformis. Gastrochena mytiloides. 
i G. modiolina. 
FAMILY III. ’ 
Sorenea. Four genera. 
1. Genus Solen. PI. VI. 
Animal. Body cylindroid, much elongated; the mantle in 
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. ‘Twenty-one species. 
Solen vaginus. Solen antiquatus. 
S. corneus. S. vaginoides. 
S. pygmeus. S. siliqua. 
S. ambiguus, S. cultellus. 
S. Dombeii. S. planus. 
S. Javanicus. S. constrictus. 
S. Caribeus. S. coarctatus. 
S. violaceus. 
S. ensis.* S. centralis.* 
S. minutus.* S. rostratus.* 
S. viridis.* S. giganteus.* 
2. Genus Panopea. Pi. VI. 
Animal. Unknown. 
The situation of the ligament, and the prominency of the 
apex, are the characters which distinguish it from the Mya. 
Shell. Regular oval, elongated, gaping at both ends, equivalve, 
inequilateral ; summit little marked and anterodorsal ; hinge com- 
