134 KANSAS UNIVERSITY QUARTERLY. 



more elevated in Meek's si3ecimen. In respect to other characters 

 the forms are closely analogous. 



I'iu'o hit if/lit i. n. sp. Plate XXXI, figs. 7, 9. 



Shell small, long, narrow, very convex. The hinge line is long and 

 straight. The dorsal border is nearly straight and the dorsal slope 

 very abrupt. The ventral border is slightly convex and the slope not 

 so abrupt as the dorsal. The posterior margin is sharply rounded. 

 The beaks are unknown. The shell surface slopes gradually from the 

 area of greatest convexity to the posterior margin and more abruj)tly 

 toward the anterior margin. The surface of the shell is ornamented 

 by regularly arranged concentric lines of growth. 



Dimensions: Length, 40 mm.; width, 12 mm.; convexity, 12 mm. 



Geological horizon : This form occurs in No. 22 of the section, 

 where it is associated with Cnio loillistoni, Valvata leei, L'toplacodes' 

 veternus, etc. 



Locality: The Freeze-out Hills, Wyoming -. also Black Hills, Da- 

 kota. 



Remarks: This form was collected from the non-marine Jura in 

 the above-named horizon, and has been named in honor of Prof. Wilbur 

 C. Knight, who in company with Prof. E. H. Barbour first discovered 

 this fossil-bearing stratum. 



Unio baileifi, n. sp. Plate XXXI, figs. 4, 6, 8, 11. 



Shell medium size, convex, elliptical in general outline. The hinge 

 line is straight and of moderate length. The beaks are slightly incurved 

 and the umbonal region is somewhat flattened. The dorsal border is 

 convex, as is also the ventral. The posterior and the anterior borders 

 are nearly equally curved. The test is thick. The ventral slope is 

 abruptly rounded while the dorsal is more broadly convex. The sur- 

 face ornamentation consists of well-marked lines of growth concen- 

 trically arranged. 



Dimensions: Length, 32 ram.; width, 23 mm.; convexity, 7 mm. 



Geological horizon : This species was collected from the fossil- 

 bearing stratum. No. 22 of the section, in which it occurs associated 

 with other non-marine forms already mentioned. 



Locality : The Freeze-out Hills, of Wyoming. 



Remarks : A comparison of the Unios here described with those 

 from the Wealden of England will be especially interesting. The 

 Ciiios from the two formations have practically the same degree of 

 development and are not known from any older rocks on either conti- 

 nent. 



