370 SYSTEMATIC PALEONTOLOGY 



convex, the latter most strongly so, while the lateral edges are sharp and 

 the ventral one generally deeply serrate, although a few specimens have 

 been noticed without the serrations, perhaps from wearing. The margin 

 of the valve is bordered by a thickened rim, within which there is often a 

 slightly depressed channel. Surface of the crust smooth, or very finely 

 granulose." Hall and Whitfield, 1875. 



Occurrence. MARTINSBURG SHALE (Eden division). Southern Penn- 

 sylvania and on the west slope of Rickard Mountain in Maryland. 



Collections. Maryland Geological Survey, TL S. National Museum. 



Genus ULRICHIA Jones 

 ULRICHIA BIVEETEX (Ulrich) 

 Plate LY, Fig. 32 



Leperditia bivertex Ulrich, 1879, Jour. Cincinnati Soc. Nat. Hist., vol. ii, 



p. 11, pi. vii, figs. 5, 5a. 

 Ulrichia f Uvertex Ruedemann, 1912, New York State Mus. Bull., No. 162, 



p. 120, pi. ix, figs. 11, 12. 



Description. " Length, 1.00 mm. ; breadth, .75 mm. Carapace minute, 

 subrenif orm ; dorsal margin straight, over two-thirds as long as the entire 

 length of the valve; anterior and posterior extremities equal in width; 

 ventral curve nearly uniform. Valves strongly convex. Tubercle at the 

 anterior end, near the dorsal margin large, rising abruptly, obtusely 

 rounded, and slightly directed posteriorly. Posterior tubercle situated 

 near the dorsal margin, and about half the length of the valve from the 

 posterior extremity, less obtusely rounded, and more prominent than the 

 anterior tubercle. Between the tubercles there is a deep sulcus, extending 

 from the dorsal margin to one-half the distance across the valve. Surface 

 smooth. On the interior there is a corresponding pit for each tubercle, 

 and a divisional ridge between them." Ulrich, 1879. 



Occurrence. MARTINSSURG SHALE (Eden division). Jordans Knob, 

 one and one-half miles northeast of Fort Loudon, Pennsylvania. 



Collection. U. S. National Museum. 



