50 Brachiopoda of the Cincinnati Group. 



Found in the upper part of the Cincuinati Group, at Richmond, 

 Indiana, Freeport, Oliio, and many other localities, at an elevation of 

 about 700 feet. It can hardly be called rare, though it is not by any 

 means abundant. 



Hemipronites sinuata — (Emmons, 1855). 



Shell semi-circular, moderately convex ; valves nearly equal, the 

 dorsal most convex in the central and anterior regions and the ventral 

 near the umbo ; hinge nearly or quite equaling the greatest breadth ; 

 margins rounding regularly to the front, whicli forms a semi-circular 

 curve with rarely a slight sinuosity at the middle. 



Dorsal valve flat at the beak, which is not distinct from the cardinal 

 margin, raised in the middle at the front, so as to form a low, broad, 

 undefined mesial prominence ; cardinal area narrow and inclined back- 

 ward. Interior with a low, small, deeply bipartite cardinal process, 

 from which diverge three small ridges, the two lateral of which extend 

 obliquely outward, to form the margins of the rather well defined 

 sockets for the reception of the teeth of the other valve, while the 

 third ridge is central, and extends a short distance forward ; muscular 

 scars not visible. 



Ventral valve moderately convex at the umbo, perforated at the 

 beak, with a broad, shallow, undefined depression at the front ; lat- 

 eral regions more or less flattened ; cardinal area well developed, ta- 

 pering to the lateral extremities, flat, and inclined obliquely back- 

 ward ; foramen closed by a prominent, triangular deltidium. Interior 

 showing a somewhat saucer-shaped cavity, formed by the low, sharp 

 dental laminae extending forward from the inner side of the rather 

 well developed, oblique cardinal teeth, and curving a little toward each 

 other, without meeting at their inner ends ; muscular scars not vis- 

 ible. 



Surface of both valves ornamented with rather coarse radiating 

 striae, most of which bifurcate once or oftener, while occasionally a 

 shorter one is intercalated ; crossing the whole are occasionally con. 

 centric marks of growth and finer striae, which are visible only with the 

 aid of a magnifier. 



Length of a medium specimen, 0.65 inch ; breadth, 0.88 inch ; con- 

 vexity, 0.20 inch. 



Found about 320 feet above low water-mark, at Cincinnati, near 

 Avondale pike, and at other places, though not common. 



Pi'of. Meek described this species in the Ohio Paleontology under 

 the name Strophomena sinuata (James), with a doubt as to whether or 



