Stegosaurus priscus, sp. nor. 



149 



Although the tibia is imperfect at its proximal end its length, can be 

 estimated at 57-60 cm. 



Since, as already mentioned, the femur of St. priscus measures 

 90 cm. in length, the ratio of these two bones in this species is 2 : 3, 

 while according to Marsh's figures it is something like 7 : 4" in 

 St. ungulatus. 



Fig. 7. Anterior view of tibia and fibula of St. priscus. 



The ratio between humerus and femur is : 1 : 2 - 3 in St. ungulatus; 

 5 : 9 in St. priscus ; 4 : 5 in 0. armatus. Thus, in the length of 

 the limb-bones St. priscus is intermediate between the two other 

 forms. 



Pelvis. — With the help of Mr. D. M. S. Watson, of Manchester, 

 three most unpromising pieces of bone have been made out to 

 represent pieces of the ilia. The left post-acetabular process and 

 portions of the margins of both ilia just near the acetabulum are 

 present. Though not very characteristic and rather crushed, the 

 post-acetabular process agrees in its slender shape rather with 

 0. Lennieri and armatus than with Stegosaurus, but the absence 

 of the rest of the ilium is to be regretted all the more, since this 

 bone is the most characteristic for separating the genera Omosaurus 

 and Stegosaurus. 



