1910.] 



NATURAL SCIENCES OF PHILADELPHIA. 



487 



A NEW HAITIAN OLIGOCENE HORIZON. 





BY HENRY A. PILSBRY. 



Messrs. W. W. Webster and Edmond Roumain, in the course of 

 explorations in Haiti in 1905, located several beds of fossils, all appar- 

 ently of Oligocene age. 



The number of species obtained is not sufficient for any comparison 

 with the Santo Domingo beds, yet the diversity of what were found 

 may indicate a slightly different horizon. The following forms have 

 been identified from a bed exposed in a stream on the road between 

 Las Caobas and Hinche. 

 Potamides roumaini n. sp. Fig. l. 



The shell is conic, rapidly and regularly tapering, rather thick and 

 solid. The summit is lost in adults, the breach 

 closed by a strongly convex plug. 6^ whorls 

 remain, sculptured as follows: each whorl bears 

 three strong spiral ridges, of which the upper one, 

 forming a projecting ledge immediately below 

 the suture, is strongest, the others equal, and 

 nearly as wide as the intervals, which are marked 

 with growth-lines. On the first two whorls the 

 ridges are made nodose by rather close longitu- 

 dinal waves, but on the last three whorls the 

 ridges are smooth and even. The last whorl has 

 about six smooth ridges below the subsutural 

 ledge, and a few very weak ones on the base. 

 The aperture is trapezoidal, channelled at both 

 ends. Outer lip thick, expanded, protruding 

 below. Columella short, thick. 



Length 24, diam. 13 mm. 



Potamides hillsboroensis (Heilprin) has some resemblance to this 

 species, but it is more nearly related to P. suprasulcatus (Gabb), from 

 which P. roumaini differs as follows: it is a smaller and narrower 

 shell ; the subsutural cord is more prominent ; the other spiral cords 

 are stronger. 



Potamides roumaini is named in honor of Mr. Edmond Roumain 

 of Port-au-Prince. In a second specimen 1\ whorls remain. 



Pota m ides ro u m aini. 



