Brachiopoda of the Cincinnati Group. 47 



by a short, mesial ridge coming from the base of the cardinal process; 

 while near the middle of the anterior edge of each there is sometimes 

 an oblique prominence ; central region, in front of the muscular im- 

 pressions, showing four obscure parallel ridges running directly for- 

 ward, and separated from each other by three shallow, narrow furrows, 

 in the middle of each of which there is a raised line ; the other parts 

 of the internal surface are marked with granulations and obscure 

 ridges. 



Ventral valve nearly flat, Avith a backward slope in the umbonal re- 

 gion, and distinctly concave further forward, in the anterior central 

 region ; anterior and lateral margins abruptly curved downward, par- 

 allel to those of the other valve ; beak scarcely distinct from the mar- 

 gin of the area, which is sublinear flat and extends the entire length 

 of the hinge ; foramen trigonal and covered by the convex pseudo- 

 deltidium, which is sinuous on its inner edge for the reception of the 

 cardinal process, and a kind of pseudo-deltidium of the other valve 

 formed by the continuation of the socket plates. Interior with the 

 anterior and lateral margins geniculated, so as to form a marginal ridge 

 that is deeply and somewhat regularly furrowed across, while the 

 ovarian spaces within this marginal ridge are more or less flattened and 

 granulated; hinge teeth moderately prominent, transversely subtri- 

 gonal, and striated on their anterior and posterior faces ; dental ridges 

 extend forward and curve together, so as to form an elevated margin 

 to the deep subcircular cavity for the reception of the muscular im- 

 pressions ; muscular cavity reaching near the middle of the valve, with 

 its rim slightly notched (not emarginated) at the middle of the front ; 

 slender mesial ridge in the bottom, with narrow adductor muscular 

 scars on each side. 



Surface of both valves ornamented with fine radiating striae that in- 

 crease by intercalation, and concentric strise which are visible only 

 with the aid of a magnifier. 



Length of a mature specimen, 0.80 inch ; breadth, 0.90 inch ; con- 

 vexity, 0.50 inch. 



Found in Warren and Clinton counties, in the upper part of the 

 Cincinnati Group, between 500 and 700 feet above low water, at Cin- 

 cinnati. Not yet known in Indiana in the same range. 



For Hemipronites elongata (James) see vol. 1, page 240, of this 

 Journal, July, 1874. 



