92 KANSAS UNIVERSITY QUARTERLY. 



Measurements: 



Length 35 mm 



Width 15 " 



Heigh 1: 05 " 



Locality: Solomon river, near Beloit, Kansas. 



Geological horizon: Ferruginous sandstone beds of Dakota Cre- 

 taceous. 



Remarks. — This form seems to differ in many respects from any of the already 

 described species of the genus, Modio/a, but as I have collected only one specimen 

 which has its characteristics so well preserved as to warrant description I hesitate 

 to establish a species on such evidence. 



Corbula, sp. Plate XX, Fig. 5. 



The shell represented on the plate by figure 5 is apparently a 

 much larger form than any of the described species under the 

 genus Corbula. So far, however, as the characteristics of the shell 

 can be made out they point to its position as being under that 

 genus. As its specific characteristics cannot be properly judged 

 from the single specimen in my possession, and as it would be folly 

 to found a determination on such meagre evidence, I prefer simply 

 to mention its occurrence. The form was found in the nature of 

 an impression in a sandstone taken from the Solomon river at 

 Beloit, Kansas. It occurs associated with Modiola sp. in the 

 Ferruginous sandstone of the Dakota Cretaceous. 



Ostrea incurva, n. sp. Plate XXII, Figs, i, 3, 5, 6. 



Shell (right valve), medium size, thin, convex, length equal to 

 twice the width, convexity increasing slightly from umbonal to cen- 

 tral region, then decreasing gradually to posterior margin; exterior 

 surface smooth, not marked by laminations or lines of growth ex- 

 cept near dorsal border; interior of shell smooth, muscular impres- 

 sion near ventral border in central region; anterior border short, 

 forming a slightly convex curve; dorsal border irregular but form- 

 ing on the whole a moderately convex curve; ventral border near- 

 est beak almost straight, but in the posterior part forming a con- 

 vex curve; beak possessing a truncated area and curved ventrally; 

 borders on each side of beak marked by small transverse ridges; 

 the dorsal side' of shell presents an abrupt slope while the slope of 

 the ventral side increases in steepness toward the beak and is 

 marked by one or more ridges with intervening depressions. The 

 postero- ventral region possesses little or no convexity; is nearly 

 flat. 



Measurements: 



