OP CONCHOLOGT. 15 



AmpMdesma cequalis, Say, Tuomey and Holmes. — Pliocene 

 Foss. of S. Carolina, p. 93, pi. 23, fig. 3. 



Observations. — This Miocene fossil has hitherto been consid- 

 ered identical with Say's cequaNs, but it differs in attaining a 

 larger size, and more especially in having a much wider cartilage 

 fosset and more elongated or produced anterior side. 



ANATINID^. 

 LEPTOMYA, Conrad. 



Description. — Elongated, inequivalve, thin, perlaceous, gaping 

 anteriorly ; hinge with a projecting spoon-shaped cartilage pro- 

 cess, narrowing gradually towards the inferior end, which is 

 acutely rounded ; this process joins an oblique callosity which 

 extends to the cardinal margin ; an obsolete rib and fissure run 

 obliquely from the anterior side of the apex. 



Periploma applicata, Conrad. — Journ. Acad. Nat. Sciences, 

 Vol. IV., 2d series, p. 276, pi. 46, fig. 1. 



This genus, which is allied to Anatina, differs from it in having 

 a tapering cartilage process attached to a rib or support which 

 joins the hinge margin anteriorly ; and in having the fissure 

 anterior to the apex, and running obliquely towards the anterior 

 extremity of the ventral margin. 



This genus is known in this country only by one species, which 

 is found in the Ripley Group of the Cretaceous era. Judging 

 from external characters and outline of the shells, I should sup- 

 pose that d'Orbigny's Periploma Rohinaldina, P. Necomiensis 

 and P. simplex are species of Leptomya^ which genus probably 

 became extinct with the Cretaceous fauna. 



The gape of the anterior is moderate, and valves but slightly 

 reflexed, in which respects it differs essentially from Anatina. 



SOLENIDiE. 

 LEPTOSOLEN, Conrad. 



Description. — Elongated, thin in substance, straight with the 

 dorsal and ventral margins parallel ; plicated anteriorly ; open 

 at both ends ; beaks not nearly terminal ; hinge of the right 

 valve with one direct tooth, convex anteriorly, truncated behind ; 

 an internal rounded direct rib commences under the cardinal 

 margin, gradually becomes less prominent and disappears towards 

 the ventral margin. 



Siliquaria hiplicata^ Conrad. — Journ. Acad. Nat. Sciences, 2d 

 series, Vol. III., p. 324, pi. 34, fig. 17. 



