96 KANSAS UNIVERSITY QUARTERLY. 



Pseudo-perna rugosa, n. sp. Plate XXIII, Figs, i, 2, 3, 4, 5. 



Shell (right valve), small, moderately thick, ovate, convex, line 

 of greatest convexit)- forming an oblique angle; umbonal region 

 smooth, surface of shell rising gradually from beak to dorso-central 

 region, thence sloping to ventro-posterior border; postero-dorsal 

 slope marked by deep grooves formed by concentric lines of growth; 

 inner surface smooth; test of practically the same thickness 

 throughout the entire extent of the shell; beak turned toward the 

 ventral border; hinge line long, possessing near the beak trans- 

 verse ridges which are rounded and separated by slight depressions. 



The ventral border of the shell is straight. The dorsal and the 

 posterior borders form parts of the same curve which presents itsj 

 greatest convexity in the mid-dorsal region. The muscular impres- 

 sion is large and ornamented by several sets of concentric striK. 



Measurements: 



Length 35 mm] 



Width 25 ' 



Height 10 ' 



Locality: Outcrop near Burr Oak, Jewell county, Kansas. 



Geological horizon: Rudistes beds, Niobrara Cretaceous. 



Remarks. — I thing the figures on the accompanying plate represent three stages] 

 in the individual development of this species. Fig. 3 represents a very young m^j 

 dividual. Figs, i and 2 represent two views of an older one, while 4 and 5 areJ 

 views of an adult. The adult form of the type has on the internal surface certain] 

 star-like forms which seem to be Crustaceans, but I have been unable to find any- 

 thing analogous to them in the literature of palaeontology. 



Pseudo-perna torta, n. sp. Plate XXIII, Figs, 6, 7. 



Shell (right valve), ovate-triangulate to oblong, almost flat, 

 slightly convex in umbonal region; beak not prominent; test thin;! 

 posterior border reflex and crenulate in some individuals; dorsal! 

 border crenulate in some individuals, attributed to accident of 

 growth; exterior surface of shell smooth or in some individuals] 

 marked by fine lines of growth; interior surface smooth. 



The hinge line is not prominent but possesses near the beak a| 

 few rounded ridges extending across the edge of the border, with] 

 no ligamental groove as in the last species. 



The ventral border varies from convex to almost straight; dorsal] 

 border also nearly straight; posterior border broadly rounded; an- 

 terior border varying from angular to broadly rounded. 



Lower valve thin, greatest thickness near margin, nearly flat,] 

 shell attached apparently by the entire under surface of the valve. 



Measurements: 



