372 DESCRIPTIONS OF NEW SPECIES OF FOSSILS 



Length, 3| ram. 



This shell belongs to the most typical form of the genus, that of D. denticulatas. 

 The series contains specimens of both valves, showing the hinge perfectly. Not 



common. 



SEMELE, Schum. 

 S. VARIEGATUM, Lam., sp. 



Tellina id., Lam., A. S. Y., v. 5, p. 490. 



Semele id., Tryon, Journ. Conch., vol. 4, p. 122. 



Only distinguishable from recent specimens from the coast of Brazil, in being 



a little thinner, and in some unimportant details of sculpture not of specific 



value. 



VENUS, Linn. 



V. RUGOSA, Gmel., Syst. Nat., p. 3216. 



Common, both living in the West Indies, and fossil. 



Y. PAPHiA, Linn., Syst. Nat., p. 1129. 



Like the preceding, found common in the West Indian waters. 



CALLISTA, Poli. 

 C. MACULATA, Linn., sp., Syst. Nat., p. 1132. 



The broad form of this common species is one of the most abundant fossils in 

 the deposit. Associated with this is another form, having all of the specific 

 characters of maculata, except that it is regularly sloping posteriorly from the 

 beak, so that the posterior cardinal margin is a nearly straight line, instead of 

 being distinctly humped. The colors are retained on one or two specimens, and 

 consist of two broad bands of irregular spots radiating downwards and backwards 

 from the beak, in the same manner as two similar bands occur on some specimens 

 of the living C. maculata. The difference in form would be amply sufiicient to 

 divide the fossils into two well-marked species, but there are specimens of C. 

 maculata from the West Indies in the museum of the Philadelphia Academy of 

 Natural Sciences which nearly, if not perfectly, connect the two forms. For the 

 cuneate form I propose the varietal name of cuneata. 



'•'■Ci/thered'^ planivieta, Guppy, is intermediate between the two in form, but can 

 be at once distinguished by its strong concentric ribs. 



MERETRIX, Lam. 

 ? M. DiscoiDEA, n. s., PI. 4t, fig. 75. 



Shell small, nearly equilateral, length and width about equal, rounded sub- 

 quadrate ; beaks central ; lunule obsolete, surface marked only by striae of growth. 



