1912.] NATURAL SCIENCES OF PHILADELPHIA. 515 



Santo Domingo Oligocene, but that is a far more ponderous and 

 long-beaked species. 



Crassatellites reevei Gabb. PI. XXIII, fig. 5. 



Crassotella antillarum Reeve? = C. reevei Gabb, Topography and Geology 

 of Santo Domingo, p. 252. 



The shell is rather long, length over 1^ times the alt., anterior 

 end rounded, posterior end long, tapering, obliquely truncate at 

 the end. Beaks at the anterior third of the length. Ridge from 

 beak to post-basal angle is moderately prominent, broad and rounded, 

 and with the posterior slope above it has sculpture of growth- 

 lines only. A distinct angulation runs from beak to the upper pos- 

 terior angle. The escutcheon is moderately deep and flat, defined 

 by a ridge. A broad, shallow concavity terminating in a sinuation 

 of the basal margin precedes the post-basal ridge. The rest of the 

 surface is convex, closely, almost regularly costate concentrically, 

 the riblets about equal to their deep intervals. This sculpture 

 extends without irregularity upon the beak, which is rather flat- 

 tened. 



Length 56, alt. about 37, semidiameter 11 mm. 



This specimen was first identified by Gabb as perhaps C. antil- 

 larum Reeve, a recent species differing conspicuously in sculpture 

 and shape. No description has been published hitherto, Gabb's 

 notes being quite insufficient for identification. 



The type, Coll., A. N. S. P., is a right valve, collected by Gabb in 

 Santo Domingo. 



Crassatellites mediamericanus n. sp. PI. XXV, figs. 3-5. 



Crassatella madropsis Con., Gabb, Journ. Acad. Xat. Sci. Phila., VIII, 

 p. 345, pi. 44, fig. 20. Not Grateloupia mactropsis Conrad. 



The shell closely resembles C. reevei Gabb, from which it differs 

 in the following particulars. The posterior end is broader, tapering 

 much less; the terminal truncation is less oblique; no angulation 

 runs to the upper posterior angle of the valve. Finally, there are a 

 couple of concentric waves of much greater amplitude defining 

 the umbonal area, which bears about 5 small waves. In C. reevei 

 there is no such irregularity in the sculpture. 



Length about 53, alt. 41, diameter .25 mm. 



Sapote, Costa Rica, in a bed considered Miocene by Gabb. Co- 

 types Coll., A. N. S. P. 



Two imperfect individuals from Gabb's collection are figured, 

 pi. XXV, figs. 3, 4. We refer also to this species a shell, pi. XXV, 

 fig. 5, imbedded in hard matrix from the Pecten bed at Tower N, 

 Culebra Cut. 



