42 CONCHOLOGY. 



equivalve, subequilateral, with summits a little marked ; hinge 

 dorsal, formed by a cardinal tooth ; two long muscular impres- 

 sions, one short primary cleft tooth in each valve, with an oblong 

 groove divided in the middle of the margin, ligament internal, 

 inserted in a pit. Two species. 



Ungulina oblonga. Ungulina transversa. 



6. Genus Solemya. 



Jlnitnal. Unknown. 



Shell. Covered with a thick epidermis, enclosing it entirely 

 except at the extremities, regular, somewhat thick, oval, elongated, 

 straight and parallel edges, also rounded at its two extremities, 

 valves equal, very inequilateral ; the anterior side much longer 

 than the posterior ; summits feebly marked ; hinge subsimilar, 

 formed by a cardinal tooth, dilated, compressed, and a little reflexed 

 above ; subexterior ligament inserted upon the tooth, and nearly 

 at the posterior extremity of the Shell ; two small, rounded, widely 

 separated muscular impressions, without any visible abdominal 

 impression. Two species. 



Solemya australis. Solemya mediterraneao 



7. Genus Amphidesma. 

 Animal. Very imperfectly known. 



Shell. Transverse, inequilateral, somewhat rounded or sub- 

 oval ; sides slightly gaping ; hinge with one or two cardinal teeth, 

 and a narrow groove for the internal ligament ; ligament double, 

 the external one short, the internal one fixed in the internal 

 grooves. The two ligaments distinguish this genus from all other 

 bivalves. Inhabits the West Indian seas. Thirty-six species. 



Amphidesma variegatum. Amphidesma Tenuii. 



A. donacillum. A. purpurescens. 



A. lacteum, A. nucleolum, 



A. corneum. A. physioides. 



A. albellum. A. pulchrum. 



A. flexuosum. A. pallidum. 



A. prismaticum. A. formosum. 



A. phaseolinum. A. roseum. 



h.. corbuloides, A. ellipticum. 



