154 



a peculiar form. It is a stout bone, but more slender than the humerus. 

 The shaft is contracted and subtrilateral in section. The extremities are 

 flattened, expanded in directions transverse to each other; the proximal 

 having, however, a lesser expansion in the plane of the distal end. The 

 former has, therefore, the form of an equilateral spherical triangle ; the apex 

 inclosing a lateral fossa, and representing probably the great trochanter The 

 distal extremity is a transverse and convex oval. This bone is either ulna, 

 femur, or tibia, judging by form alone. Its greater length, as compared with 

 the fibula, forbids its reference to the last; the trochanter-like process of the 

 head is exceedingly unlike any examples of the second bone I have seen. 

 Its reference to femur is confirmed by its presence with the caudal vertebrae 

 of a similar species from near the Missouri River, Nebraska, and its resem- 

 blance to the femur of Liodon dyspelor. 



Measurements. 



M. 



Length of the humerus 0. 100 



Proximal diameter of the humerus 0. 095 



Distal diameter of the humerus 0. 102 



Length of the femur 0. 080 



Proximal diameter of the femur 0. 065 



Median diameter of the femur 0. 035 



Length of the centrum of a dorsal vertebra without the hall 0. 061 



Transverse diameter of the cup 0. 060 



Vertical diameter of the cup 0. 053 



Length of a lumbar (total) 0. 050 



Diameter of the ball of a lumbar (transverse) 0.060 



Length of a caudal 0. 041 



Depth of the hull of a caudal 0.052 



Width of tho ba!l of a caudal 0.052 



The form of the humerus is something like that of Ichthyosaurus. Both 

 this element and the femur are remarkable for their small size. They are 

 scarcely half the dimensions of the elements of the anterior limb of Plate- 

 carpus ictericus; and are even less than those of L. dyspelor in proportion to 

 the animal's size 



Some of the ribs preserved exhibit cylindric shafts. 



The form of humerus nearly resembles that of P. simus as figured by 

 Professor Marsh, and it is probable that these species are very nearly allied. 

 The vertebra; indicate the largest of >pecies of this genus. 



The remains above described were obtained by Prof. B. F. Mudge, near 

 Eagle Tail, in Colorado, a few miles west of the line separating that Terri- 

 torv from the State of Kansas. 



