CRUSTACEA— OSTRACODA. 349 



angular; length one and one half to one and three fourths times 

 height. (Type of genus.) 



Stones River of Minnesota and Cincinnati region. 



XVIII. JoNESELLA Ulrich. 



Small oblong or subovate Ostracoda, distinguished by a curved 

 ridge on the posterior two thirds. Four species. Ordovicic. 



38. J. crepidiformis Ulrich. (Fig. 1658, a-c.) Ordovicic. 

 Curved ridge U-shaped; carapace convex. 



Lower Cincinnatian of Kentucky. 



39. J. pedigera Ulrich. (Fig. 1658, c/, ^.) Ordovicic. 

 Curved ridge crosier-shaped ; long arm at ventral border. 



XIX. DiCRANELLA Ulrich. 



Distinguished from Ulrichia in having one or both nodes devel- 

 oped into long horn-like diverging prominences. Five species. 

 Ordovicic. 



40. D. bicornis Ulrich. (Fig. 1657, ;, ^.) Ordovicic. 

 With two well developed horn-hke prominences, diverging at 



an acute angle and rising above hinge line; a pronounced ridge 

 runs parallel to margin. (Type of genus.) 

 Stones River and Black River of Minnesota. 



XX. Drepanella Ulrich. 



Depressed-convex, suboblong valves with a more or less com- 

 plete, often sickle-shaped, sharply elevated marginal ridge, within 

 which the surface exhibits two or more usually distinct nodes; 

 ventral edge thick; size usually 2.5 mm. by 1.5 mm. Eight species. 

 Ordovicic. 



41. D. crassinoda Ulrich. (Fig. 1657, /-n.) Ordovicic. 

 Outer ridge close to margin slightly interrupted anteriorly; two 



large and one small (anterior) vertical nodes, and a short longi- 

 tudinal one in anterobasal portion, (Type of genus.) 

 Stones River of Kentucky. 



42. D. elongata Ulrich. (Fig. 1657, 0.) Ordovicic. 

 Elongate ; outer ridge some distance from margin, absent at 



