434 Systematic Paleontology 



Anoplotiieca concava (Hall) 

 Plate LXXIII, Figs. 18, 19 



Leptoccelia concava Hall, 1857, Tenth Ann. Rept. N. Y. State Cab. Nat. Hist., 



p. 107. 

 Leptoccelia concava Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 245, pi. xxxviii, 



flgs. 1-7, 1861. 

 Coclospira concava Clarke, 1900, Mem. N. Y. State Mus., vol. ill. No. 3, p. 42, 



pi. V, figs. 23-26. 



Description. — " Shell ovate or suborbicular : ventral valve convex, ele- 

 vated along the middle into a mesial prominence, which extends to the 

 umbo; beak small, incurved beyond the hinge-line: dorsal valve [flat- 

 tened] near the lateral margins, depressed in the middle, forming a 

 shallow undefined sinus M'hich is deeper in tlie center than at the front, 

 and rapidly diminishes towards the umbo; beak straight : area small; fora- 

 men triangular and extending to the apex of the beak, sometimes closed 

 below by a deltidium. Surface marked by fourteen to seventeen striae, 

 which sometimes bifurcate : the one on the middle of the mesial fold of 

 the ventral valve is generally smaller than the others, giving a slightly 

 grooved appearance along its center quite up to the beak." Hall, 1857. 



Length 6 mm. ; width 7 mm. 



The Maryland specimens agree very well with New York material, and 

 the only noticeable difference is that the former have fewer strige, i. e., 

 from twelve to fifteen instead of from fourteen to seventeen. 



Abundant in the New Scotland member of Allegany County. 



Occurrence. — -Helderbehg Formation, New Scotlaxd Member. 

 Corriganville, Devil's Backbone, Dawson, Maryland; Cherry Eun, West 

 Virginia ; Warren Point, Pennsylvania. Becraft Member. Warren 

 Point, Pennsylvania. 



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



Anoplotheca concava var. tonolgv^^ayensis n. var. 

 Plate LXXIII, Figs. 20, 21 

 Description. — Shell small, ovate, greatest width at or near hinge-line. 

 Ventral valve convex; mesial elevation pronounced near umbo, becoming 



