Maryland Geological Survey 159 



on each side of the beak. Ordinary spines have not been observed on any 

 other specimens referred to this species. 



Occurrence. — Romney' Formatigk, Onondaga Member. Williams 

 Road 31/2 miles southeast of Cumberland. 



Collection. — U. S. ^Mational Museum. 



[E. M. Kindle.] 



Genus ANOPLIA Hall and Clarke 



Anoplia nucleata (Hall) 



Plate XIII, Figs. 10-13 



Leptaena nucleata Hall, 1857, Tenth Rep. N. Y. State Cab. Nat. Hist., p. 47. 

 Leptaena f nucleata Hall, 1859, Pal. N. Y., vol. iii, p. 419, pi. 94, fig. 1. 

 Anoplia nucleata Kindle, 1912, Bull. U. S. Geol. Surv., No. 508, p. 73, pi. v, 

 figs. 8-11. 



Description. — Shell small, concavo-convex, and strongly arched. Sur- 

 face without striae or plications. Interior of both valves strongly pustu- 

 lose. Ventral valve very gibbous in the umbonal and median region, beak 

 incurved. In the interior a strong septum extends from the beak about 

 one-third the distance to the front of th^ shell. In nearly all specimens 

 this septum terminates abruptly. In a few individuals, however, it is 

 continued forward a short distance beyond its normal terminus as a pair of 

 rather faintly developed, divergent, y-shaped arms. Most of the specimens 

 from Mendota,, Virginia, show moulds of the spine tube. This extremely 

 slender tube originates on the inner surface of the shell, midway between 

 the beak and the cardinal angle just inside the inner margin of the area, 

 and crosses diagonally the marginal portion of the valve with a slight 

 curve. It terminates at the side of the beak in a minute point apparently 

 not reaching the outer surface of the shell. 



Dorsal valve moderately and regularly concave. Outer surface marked 

 by a minute tripartite median process just inside the hinge-line. This 

 comprises two short divergent lobes and a third median lobe stronger than 

 the lateral one, having a lengih of about % of a mm. The interior of this 

 valve is characterized by two slender sharp median ridges. These diverge 

 slightly as they extend forward from the base of the cardinal process and 

 terminate about % the distance from the hinge-line to the front. A 



