390 SlSTEilATTC r.VLEONTOLOGY 



genus, 0. navicella Hall and Clarke, 0. slnuaia Clarke, and 0. lucerna 

 n. sp. 



Oriskania lucekna n. sp. 

 Plate LXVII, Figs. 20-24 



DescHption. — This species is most nearly related to 0. sinuaia, but 

 differs in having a very prominent, ventral, false cardinal area which is 

 decidedly curved dorsally, the dorsal valve is flatter or slightly concave 

 and not sinuate, lateral commissure straight or concave and not sigmoid, 

 and the outline of the shell is more quadrangular. In Avell-preserved 

 specimens the exterior is marked with exceedingly obscure radial striae 

 of the same nature as in Beachia. 



Mr. Eoeder has two specimens of what appears to be this species, in 

 which the dorsal valve is evenly convex and the lateral margins inflected 

 as in R. suessana. These specimens with others more typical for 0. lucerna 

 remind one so much of R. suessana that it seems as though they must have 

 descended from the latter. 



Two specimens favorably preserved were broken open to ascertain the 

 nature of the brachidium, but nothing more than the posterior ends of the 

 descending branches was found. Evidently the brachidium is very deli- 

 cate and is not easily fossilized, or its absence is due to secondary replace- 

 ment by silica, since nearly ail the Oriskany fossils are pscudomorphs. 

 This shell in the Maryland region cannot be confounded with any other 

 brachiopod. 



Length 2.4 cm. ; width 2.1 cm. 



Occurrence. — Oriskant Formation, Eidgely Membltj. Common at 

 Eidgely, West Virginia. 



Collections. — Maryland Geological Survey, U. S. National Museum. 



Family TEREBRATELLID/E 



Genus TROPIDOLEPTUS Hall 



Tropidoleptus cari.vatus (Conrad) 



Plate LXVII, Fig. 25 



Strophomena carinata Conrad, 1839, 3d Ann. Rept. N. Y. Geol. Survey, 



p. 64. 

 Leptwna laticosta de Verneuil, 1847, Bull. Soc. Geol. France, 2d ser., vol. iv, 



p. 703. 



