0. C. Marsh—On Dinosaurian Reptiles. 487 
pelvis and hind limb, as being especially characteristic, we find 
in the existing A//igator, as represented in the diagram (figure 
2), that the pubic bone is excluded from the acetabulum 
articulating alone with the ischium, and not at all with the 
ilium. The calcaneum, moreover, has a posterior extension. 
In Aétosavrus, as shown in the corresponding diagram (figure 
3), the pubic bone forms part of the acetabulum, as in 
Dinosaurs and Birds, and this is a noteworthy difference from 
all the existing Crocodiles. The hind foot, however, is of the 
Crocodilian type, with the caleaneum showing a posterior 
projection. 
FIGURE 7.—Diagram of pelvis of Belodon Kapfi, von Meyer; seen from the left. 
One-fourth natural size. 
a, acetabular surface, within dotted line; 7/, ilium; 7s, ischium; 
p, pubis. 
In Belodon, the pelvis of which alone is here represented 
(figure 7), the pubis contributes a very important part to the 
formation of the acetabulum, and to the entire pelvic arch. 
The latter differs from the pelvis of a typical Dinosaur mainly 
in the absence of an open acetabulum, but a moderate enlarge- 
ment of the fontanelle at the junction of the three pelvic 
elements would essentially remove this difference. A more 
erect position of the limb, leading to a more distinct head 
on the femur, might possibly bring about such a result. The 
feet and limbs of elodon are Crocodilian in type. 
