252 



ON THE TOPOGRAPHY AND GEOLOCIY 



MYSIA. Leach. 



H. capuloides. Gabb, n. s. 



Shell small, thin, globose, anterior nearly circular, slightly compressed across the hinge margin ; beaks small, in- 

 curved ; umbones very large, giving to single valves a form not unlike tliat of shells of Gapulus. Surface polished 

 and ornamented by minute concentric striaj. Diameter about .3 inch. 



M. s u b - q U a d r a t a . Gabb, n. s. 



Shell small, thin, moderately convex ; outline rounded sub-quadrate, length and width about equal, beaks small, 

 prominent, hinge line sloping equally oU both sides. Surface smooth. 



About the size of the preceding, but distinguished by its comparatively square 

 form and the absence of the enormous umbones. 



ERYCINxi. Reel. - . 



E. tensa, Guppy, Quart Jour., Vol. XXlI., p. 583, pi. 22, fig. 6. . . - , 



GOULDIA. Adams. 



G. Martiniconsis. D'Orb, sp. 



Crassatella, id. D'Orb, La Sagra, pi. 37, lig. 31-33. . '-^ . - ' . . . ^ . 



Gouldia, id. II. and A. Ad., Genera, Vol. II., p. 435. ... 



C. Antillarum. live., Zool. Proc, 1842, p. 44 ; Icon, sp., 8. ' ■ 



I have a single valve, well preserved and which differs from recent specimens in 

 being straighter in the lunular region, and more oblicpicly trancated behind. It is also 

 regularly marked with concentric fin-rows. The sculpture is not constant in this 

 genus, and the differences of outline are not sufficient to permit me to separate it on 

 a single specimen. If however, these differences should prove to be constant, the 

 fossil form might be separated under the name of C. Reevei, 



C. scabricostata. Guppy, Quart. Jour., VoL XXII., p. 293, pi. 18, fig. 10. 



The figure does not partake of the usual excellence of Mr. Gnppy's illustrations. 

 The shell is placed in a false position, and the correct numbei* of ribs is not given. 

 The blame, however, can hardl}'' rest upon the author since he was probably in Ti-ini- 

 dad when the plate was drawn in London. I mention the inaccuracj^ in no spirit of 

 hypercriticism, but that other students may not be misled by it. 



CRASSATELLA. Lam. 



CARDITA. P>rug. 



CRENELLA. Brown. 



C. divaricata. D'Orb., sp. 



Nuculocardia divaricata. D'Orb., La Sagra, pi. 37, fig. 56-59. 

 Crenclla-. id. 11, and A. Ad. Gen. Rec. Moll., Vol. IL, p. 515. 



MODIOLA. Lam. 



M. sp. ? 



Two minute specimens, too 



ism.all for satisfactory determination. 



