32 Brachiopoda of the Cincinnati Group. 



Dorsal valve less convex than the other, with usually a very slight, 

 scarcely perceptible mesial depression near the umbo, that rarely, if 

 ever, extends forward to the middle; beak small, projecting slightly 

 beyond the edge of the area, and merely a little arched ; area of com- 

 paratively moderate height, flat, or somewhat arched, and inclined 

 more or less obliquely backward anS upward ; foramen forming a 

 nearly equilateral triangle. 



Ventral valve most convex near the umbo, and perhaps always 

 showing a very shallow, broad, undefined mesial sinuosity at the front ; 

 b^k moderately prominent, pointed, inclined backward and a little 

 arched, but not incurved ; area comparatively rather high, or from 

 twice to three times the height of that of the other valve, well defined, 

 a little arched, and inclined obliquely backward and down warct; for- 

 amen narrow, triangular, and extending to the point of the beali. 



Surface of both valves ornamented by very fine radiating striee, most 

 of which bifurcate two or tree times between the beaks and free mar- 

 gins ; the lateral ones being moderately arched. 



Length of a medium sized specimen, 0.23 inch ; breadth, 0.28 inch ; 

 convexity, 0.13 inch. 



Found associated with 0. pUcatella and 0. fissicosta, on the hills back 

 of Cincinnati, and at the quarries at Hamilton, in Butler county, at 

 an elevation of about 350 feet above loW water-mark. It is a rare 

 fossil. 



Orthis (?) elh— (Hall, 1860). 



Shell small, ovate ; valves nearly equally convex ; hinge line ex- 

 tremely short, being scarcely more and sometimes less than one third the 

 width of the shell, and scarcely afiecting the contour of the cardinal mar- 

 gin, which slopes from the beak of the ventral to the lateral margins a 

 little above the middle of the valve. Dorsal valve gibbous, sub-cir- 

 cular ; the beak extending a little above the hinge line, and the area 

 extremely short. Ventral valve broadly ovate, sloping from the 

 beak ; beak produced beyond the line of the opposite valve, and pointed, 

 not incurved; area twice as long as high ; foramen narrow and extend- 

 ing to the apex of the beak, and sometimes truncating the extremity. 



Surface marked by from fifteen to twenty simple, abruptly rounded 

 or sub-angular plications. 



The short hinge line and area, and the produced beak of the ventral 

 valve, are characteristic features. They differ very much in size and 

 in the number of striaj. Length sometimes a little greater than the 

 breadth, and breadth sometimes a little greater than the length. 



