Description of Some Cincinnati Fossils. 



157 



Beyrichia hammelli n. sp. 



Plate S, Fig. 26, right valve magnified twelve diajneters, with a 

 small piece of the border broken away at the antero- dorsal 

 angle. 



Carapace medium size, dorsal margin straight and nearly as 

 long as the greatest length of the valves. Anterior and pos- 

 terior extremities broadly rounded, the anterior being slightly 

 the wider of the two. Greatest width of the valves at the 

 anterior third, where the width is to the length of the dorsal 

 margin about as three is to four. Basal margin rounded, and 

 slightly advancing at the anterior third. Valves moderately 

 convex, with a border on the anterior, posterior, and basal 

 margins, separated from the valve by a sharply-defined line 

 or groove. The border on the basal margin is about one- 

 sixth the width of the valve, and it narrows to about two- 

 thirds that width at the antero-dorsal angle, and to about one- 

 third that width at the postero-dorsal angle. The body of the 

 valve is constricted by two sulci, directed obliquely backward 

 from the basal border of the shell ; the anterior one arises at 

 the groove separating the border from the body of the shell, 

 at the antero-basal margin, and when half way across the 

 valve bifurcates, the stronger sulcus being directed forward 

 toward the antero dorsal margin, and the shallower one fading 

 out before it reaches the dorsal margin of the shell. There 

 is thus formed, anterior to this sulcus, a large, convex, 

 rounded area, and between the branches of this sulcus and 

 the dorsal margin a depressed, convex, subtriangular area. 

 Between the two oblique sulci there is a convex ridge more 

 prominent than the rounded area in front, and which extends 

 farther toward the basal margin than either the anterior or 

 posterior convex areas. The posterior oblique sulcus fades 

 out before it reaches the dorsal margin. The area between 

 the posterior oblique sulcus and the posterior extremity of 

 the valve is wider, but not as prominent as the more central 

 ridge between the oblique sulci. 



The surface of the valves is distinctly granulous. The 

 margin of the border, as seen on the interior side of the shell, 

 is fringed or ciliated in the same manner as Beyrichia ciliata. 



