98 Cincinnati Societij of NafAiral History. 



Ky., at an elevation not exceeding 125 feet above low water mark at 

 (Jincinuati, O. 



CRANID^E. 



Genus Crakia, Retzins. 



Crania parallela, n. sp. (Plate IV., fig. 13.) 



Shell under medium size, sub-rectangular in outline; upper valve 

 quite convex, with the apex placed generally about one fourth the 

 length of the valve, from the posterior margin. 



Surface marked, according to age of the specimen, b}^ from seven to 

 fifteen parallel, raised lines, crossing the shell from side to side; these 

 lines are generally uuiforiu, but sometimes a few stronger ones are 

 placed among them; with a magnifier, the shell is seen to be covered 

 with minute tubercles, a line of them always cresting each of the 

 parallel striiB; these tubercles form regular longitudinal rows, giving 

 to the surface the appearance of being striated in the direction from 

 the anterior to the posterior margin. 



Under valve unknown. 



The impressions of the anterior muscles are nearly united in a 

 transversely sub-elliptical scar; posterior abductor scars distant, not 

 well defined in the specimens observe 1. 



Length of large specimen, 7 m. m. ; width, 5 m. m. ; convexity of upper 

 valve, 1.5 m. m. 



In the rectangular outline, it is not unlike Crania multijninctata. 

 Miller, but the distinct puncta, and the absence of other surface 

 markings on that shell, will serve to distinguish them. 



Locality and Position. — I found the specimen on slabs of cr^-staline 

 limestone, at Covington, Ky., at an elevation of 100 feet above low 

 water mark at Cincinnati, 0. 



Crania percarinata, n. sp. (Plate IV., fig. 12.) 



Shell under medium size, ovate to sub-circular in outline. Upper 

 or dorsal valve very convex, the apex usuall}- situated about one third 

 of the length of the shell from the posterior margin ; margins thickened. 



Surface marked by three strong carina, close together, running longi- 

 tudinally across the middle of the shell, with greatest prominence at 

 the center, and becoming gradually less strong toward the ends; some- 

 times there is another ridge near the lateral margin. 



Crossing the shell laterally' are fine, thread-like striiv, which cuive 

 backward and forward, very much like the striae in Jfurchisonia; near 

 the margin of the valve are a few, slightly stronger concentric lines. 



Ventral valve unknown. 



The interior of the dorsal valve shows the anterior impressions of 



