378 DESCRIPTIONS OF NEW SPECIES OF FOSSILS 



PINNA, Linn. 

 P. RTjDis? Linn., Enc. Metli., PI. 19 J, fig. 3. 



A single imperfect valve, too poor for a positive identification. 



ARCA, Linn. 

 A. IMBRICATA, Brug., Enc. Meth., p. 98. 



Common. Although this shell was said to come from the South Sea, our fossil 

 is identical with recent specimens of the West Indies, which seem without doubt 

 to be Bruguiere's species. 



A. (Andara) Deshaysii, Hanley, Sp. of Shells, p. 155. 



A well known West Indian species. 

 A. (A.) CONSOBRINA, Sby., Quart. Journ. Geol. Soc, London, v. 6, p. 52, PI. 10, fig. 12. 



Described from the Santo Domingo Miocene by Sowerby, and since found in the 

 same formation in Jamaica. 



A. (A.) GRANDis, Brod. and Sby., Zool. Jour., v. 4, p. 365. 



A. patricia, Sby., Q. J. G. Soc, v. 6, p. 52. 



A. Chiriquensis, Gabb, Proc. Phila. Acad., 1860, p. 56T. 



But a single young shell was found, but it is identical with specimens of the 

 corresponding age found by me in the Santo Domingo beds. Sowerby's attempt 

 to divide the fossil from the living form is not sustained by my examination of a 

 large series of the fossils, and on comparing the originals of my species, I find 

 that I have been misled hy the persistence of granules on the ribs in even large 

 shells, a character which is usually not retained after the individuals acquire a 

 diameter of more than an inch. Their presence in large shells among the Chiriqui 

 fossils is probably the result of their having lived in very quiet water, as is indi- 

 cated by the extremely fine grained clay in which they are imbedded. 



AXIN^A, Poll. 

 A. SERICATA, Rye. (sp.), P. Zool. Soc, 1843, Icon., PI. 9, fig. 43. 

 Very abundant fossil ; living in the West Indies. 



NUCULA, Lam. 

 N. LiMONENSis, Gabb, n. s., PI. 47, fig. 82. 



Shell small, oblique, beaks very far in advance, posterior end cuneate ; anterior 

 end and base rounded. Hinge robust, central fosset very sunken, small and ob- 

 lique. Outer surface smooth and polished. One specimen before me shows rather 



