656 Systematic Paleoxtology — Upper Devonian 



Cypricaedella tenuistkiata (Hall) ' 

 Plate LXVI, Figs. 1-5 



The individuals observed in Maryland are somewhat longer proportion- 

 ally than is us;ial in the species in New York as shown by Hall's figures. 

 This species is characterized by having strong concentric striae on umbo. 

 It differs from C. hellistriata, in having a more acute posterior-inferior 

 angle, weaker strise save on umbo, and in hinge-tooth. It differs from C. 

 gregaria, which it closely resembles, in ha^•ing much stronger strise on 

 umbo and also in its proportions. 



Occurrence. — Jennings Formation, Chemung Member. Town 

 Creek, 2122. Parkhead Member. Williams Eoad, on Polish Mountain, 

 1660; 2 miles north of mouth of Town Creek, 1716; Town Creek, 1605; 

 2i/> miles above mouth of Sideling Hill Creek; Woodmont, 1285. 



Collection. — Maryland Geological Survey. 



Cypricardella nitidula n. sp. 

 Plate LXVI, Figs. 6-12 



Description. — Shell rather small, subcircular in outline, slightly trun- 

 cate on posterior margin, expanding somewhat posteriorly; beak anterior; 

 hinge-line curved. Surface regularly convex, with broad and low but dis- 

 tinct umbonal ridge sloping posteriorly to margin; depressed between 

 umbonal ridge and hinge ; covered with regular and, for this genus, strong, 

 rounded and continuous concentric ridges. On internal casts the cardinal 

 area appears broad and subtriangular centrally, extending backward to 

 the posterior extremity of the shell. A deep central socket in the right 

 valve is bounded by low ridges and in the left valve is a strong central 

 tooth with lateral depressions for the reception of the teeth of the other 

 valve. Anterior and posterior muscular scars well defined. Central area 

 moj-e of less decidedly marked by an oblique ridge. 



An average specimen has a length of 11 mm. and extreme height of 

 10 mm. 



^ For synonymy and description see page 275. 



