88 KANSAS UNIVERSITY QUARTERLY. 



rent. In this still water, on the floor of the sea, these forms lived 

 and died and were quickly buried by the accumulation of the bodies 

 of the protozoans which formed the chalk. 



Ostrea kansaeensis, n. sp. Plate XX, Figs, g, lo, ii. 



Shell (left valve), irregularly sub-ovate, medium in size, convex, 

 maximum convexity in central area; test thick, thickness greatest 

 at margin; external surface comparatively smooth, yet encircled at 

 irregular intervals by light stride of growth; interior of valve marked 

 by a deep fossa, in the interior region, otherwise smooth; anterior 

 border slightly curved outward; posterior border short, convex; 

 ventral border deeply concave, not entirely regular in outline curve; 

 external surface sloping in all directions and turning abruptly down- 

 ward at at the margins. 



Measurements: 



Length 30 mm 



Width 25 " 



Height 5 " 



Locality: Ellsworth county, Kansas, near Kanapolis. 



Geological horizon: Lower Cretaceous. 



Remarks. — This species is based on a number of forms collected by the writer 

 during the past summer frem the above named locality. Variability, a character- 

 istic of the species of this genus, is not so well marked in the forms of this species 

 as in some of the associated species. The individual figured is fairly representa- 

 tive of the class. It is found associated with O Wellerii and O. Willistonii. 



Ostrea ellsworthensis, n. sp. Plate XXI, Figs, i, 2. 



Shell (left valve), medium size, very slightly convex; exterior 

 surface possessing moderately heavy undulations and ribs; ribs 

 more prominent at margins but not extending in points beyond, 

 crossed at irregular intervals by lines of growth; test moderately 

 thick, thickness not uniform; beak sharp pointed, possessing a 

 small triangular area; ventral border concave; dorsal border ir- 

 regular; anterior border nearly straight and ending in the first mar- 

 ginal rib; posterior border concave, separated from the ventral 

 border by a marginal rib; interior surface marked by flextures, 

 subumbonal region containing a deep fossa on the margin of which 

 is the muscular impression. Individuals of the species free. 



Measurements: 



Length 39 mm 



Maximum width 40 " 



Height 7 " 



Locality: Coal Canon, Ellsworth county, Kansas. 



Geological horizon: Lower Cretaceous. 



