44 Brachiopoda of the Cincimiati Group. 



anterior central and lateral portions, and curving downAvard, around 

 the front and lateral margins ; area narrow, or nearly linear, and di- 

 rected obliquely backward and upward ; beak not distinct from the 

 margin of the area. 



Interior showing cardinal process short and divided into two low 

 diverging parts, directed obliquely forward and outward, and flattened 

 on their posterior faces ; socket ridges longer and stronger than in 

 planumboim ; mesial ridge low and terminating before it reaches the 

 middle of the valve. On each side of the mesial ridge and between it 

 and the socket ridges three parallel ridges start forward ; those nearest 

 the socket ridges are low and short ; those adjoining the mesial ridge 

 become stronger as the mesial ridge fades away, and form coarse strong 

 ridges as they pass the middle of the valve, and do not terminate until 

 they have nearly crossed tlie valve ; the other two ridges are not quite 

 so large, and are a little shorter than the last. Other light lines and 

 granulations in the cavity of the shell do not preserve uniformity of 

 appearance in different specimens. 



Ventral valve nearly flat, or slightly convex in the umbonal region, 

 and broadly and deeply concave in all the central and anterior central 

 parts, but curving upward around the front and lateral margms nearly 

 parallel to the free margins of the other valve ; cardinal area of mod- 

 erate height, extending the whole length of the hinge, but sloping 

 rather distinctly from the beaks laterally, flat and directed nearly at 

 right angles to that of the other valve ; beak very small, and only 

 projecting slightly beyond the margin of the area ; foramen closed by 

 the usual convex pseudo-delitidiura, which is deeply sinuous on its in- 

 ner margin, for the reception of the cardinal process of the other valve. 

 Interior with cardinal edge but slightly prominent ; hinge teeth sub- 

 trigonal, oblique, and but moderately developed ; dental ridges prom- 

 inent, strong, and encircling a rather large, deep, saucer-shaped cavity, 

 one third to one half the length of the valve, and marked within by 

 an obscure central ridge, and on each side of this by rather strong 

 radiating furrows ; anterior and lateral margins a little thickened 

 within, and divided by the crossing, apparently, of the vascular mark- 

 ings into short obscure ridges ; entire internal surface sometimes show- 

 ing, under a magnifier, a very minute, obscurely granular appearance. 



Surface of both valves ornamented by numerous fine, subequal, 

 crowded and rounded strise, that increase by intercalation. Concentric 

 stride may be seen with the aid of a magnifier, A number of strong 

 plications or wrinkles extend from the edge of the area on each side of 

 the beak on each valve a short distance at right angles to the cardinal 

 line, or slope a little inwardly. 



