40 Brachiopoda of the Cincinnati Group. 



Length of a well developed specimen, 0.96 incli; breadth, 1.30 

 inches; convexity, 0.43 inch. 



Found at Madison, Versailles, Weisburg, Richmond, Oxford, Free- 

 port, Clarksville, and generally wherever the rocks are exposed 

 within about 200 feet of the top of the Cincinnati Group. Good 

 specimens are not, however, very common at any locality, 



OrtJiis inscuJpta — (Hall, 1847). 



Shell generally rather under medium size, wider than long, sub- 

 quadrate, or transversely truncato-suboval ; hinge line nearly always a 

 little less than the greatest breadth of the valves and meeting the 

 lateral margins at an angle of usually more than ninety degrees ; 

 lateral margins generally moderately convex in outline, at or near the 

 middle, and rounding regularly to the front, which is nearly always a 

 little sinuous in the middle; valves moderately and nearly equally 

 convex. 



Dorsal valve with its greatest convexity usually a little behind the 

 middle, on each side of a narrow, but moderately deep mesial sinus, 

 that extends from the beak to the front ; posterior lateral region dis- 

 tinctly compressed ; beak but little prominent, and more or less 

 incurved ; area moderately developed, narrowing rather rapidly to the 

 lateral extremities, directed backward and more or less strongly arched , 

 foramen broad, triangular, and partly occupied by the cardinal process, 

 which usually projects slightly beyond the surface of the area and is 

 laterally compressed. Interior showing the brachial processes to be 

 rather prominent and diverging, and the sockets for the reception of 

 the teeth of the other valve distinct ; scars of the adductor muscles 

 (occlusors of some) situated on each side of a strong, prominent 

 mesial ridge, behind the middle of the valve, those of the posterior 

 pair being very narrow anterio-posteriorly, and placed back directly 

 under the brachial processes, nearly out of sight in a direct view, 

 while the anterior pair are larger, oval in form, and extend forward 

 nearly to the middle of the valve ; vascular markings consisting of two 

 principal lateral trunks, that extend outward and forward from the 

 anterior adductor scars, but immediately bifurcate, sending each a main 

 division backward and outward, and another forward, each with sub- 

 ordinate branches, while between these principal trunks there are two 

 pairs of smaller ones and traces of a few other still smaller, all directed 

 forward. 



Ventral valve about as convex as the other, but having its most 



