Maryland Geological Subvey 215 



State Paleontologist and is apparently correctly identified. This species 

 is readily distinguished by its elongate form, fine concentric striae and 

 radii with stronger radii on the umbonal ridge and anterior end. 



Occurrencp. — Romnpa' Foumation, Hamilton Membee. Williams 

 Road 3J miles soiithea;-'t of Cumberland. 



Collections. — Maryland Geological Survey; New York State Museum; 

 American Museum of Natural History. 



Family SOLENOPSIDAE 



Genus PROTHYRIS Meek 



Pkothyris lanceolata Hall 

 Plate XXI, Figs. 8-10 



Prothyris lanceolata Hall, 1883, Pal. N. Y., vol. v, pt. i, plates and expla., pi. 



Ixxvi, figs. 2-8. 

 Prothyris lanceolata Hall, 1885, Pal. N. Y., vol. v, pt. i, Lamellibranchiata ii, 



p. 460, pi. Ixxvi, figs. 2-8. 

 Prothyris lanceolata Clarke, 1903, N. Y. State Mus., Bull. 65, p. 492. 

 Prothyris lanceolata Grabau and Shimer, 1909, N. Am. Index Fossils, vol. i, 



p. 377, fig. 477e. 



Description. — Shell of medium size, elongate-lanceolate; length three 

 times the height ; basal margin very gently curving, often nearly straight 

 on the anterior half; posterior extremity pointed, very obliquely truncate 

 above; anterior end truncate, margin refle.xed, with a slight constriction 

 behind it and without any conspicuous limiting notch; cardinal line 

 about two-thirds the length of the shell. Valves moderately convex in 

 the posterior part, gibbous in the middle and umbonal portions; beaks 

 subanterior, not prominent, slightly incurved ; umbonal slope angular 

 above, extending to the posterior extremity, often merging into the 

 general convexity of the shell below the middle; post-cardinal slope 

 narrow, slightly concave. Surface marked by fine concentric striae, which 

 are sometimes somewhat fasciculate, producing gentle undulations. 



A single good specimen of the right valve of this species was found in 

 the blue shales on the West Virginia bank of the Potomac about three 

 miles south of Cumberland. The species is readily recognized by its 

 elongate lanceolate form, truncate and reflexed anterior margin with a 



