164 University of Kansas Geological Survey. 



Tibia. 



Clidastes velox. The tibia is a moderately stout bone, articu- 

 lating proximally by a thickened, oval face with the thickened 

 articular facet of the femur. It is more flattened and expanded 

 distally than proximally. The outer border is thick and rounded, 

 and concave longitudinally from near the proximal angle quite 

 to the distal articular face, which it meets in an acute angle. 

 The outer border is thin and moderately deeply concave near 

 the middle, the proximal end convex in outline, the distal end 

 meeting the long convexity of the distal border in an obscure 

 angle. The thickened face for the tarsal is on the inner third 

 of the distal border, and is placed obliquely to the long axis. 

 The articular surface is cupped and oval in outline. 



Plate-carpus . The tibia of Platecarpus resembles that of Cli- 

 dastes more than that of Tylosaurus. It is more flattened than 

 in Clidastes, less than in Tylosaurus. Its outer border is less 

 deeply concave than in Clidastes ; the articular facet for the tar- 

 sal is smaller, the inner border is longer and less deeply con- 

 cave, almost wholly lacking the convex flattened expansion 

 proximally. The curvature of the distal border does not extend 

 as far proximally. 



Tylosaurus proriger. The tibia in Tylosaurus is an exceedingly 

 broad, flattened bone, the width of the distal extremity being 

 nearly as great as the length. The outer border is gently con- 

 cave throughout, while the free, inner, thin border is confined 

 to a shallow notch on the proximal half. The outer distal angle 

 is broadly rounded, as in Clidastes, the proximal less so. The 

 proximal border is nearly straight transversely, while the distal 

 is gently convex. There is no facet for a tarsal bone. 



Fibula. 



Clidastes. The fibula in Clidastes is characteristic. It is a 

 small slender bone, with the distal extremity expanded fan- 

 shape. The outer border is the thicker, concave throughout, 

 the concavity deepest beyond the middle, the border meeting 

 each end in nearly a rectangle. The inner side is also concave, 

 the concavity deepest near the middle. The distal extremity is 



