AFFINITIES WITH CEOCODILIA. 



233 



If some of the characteristic' parts of the skeletons of these groups 

 are compared, e. g., of the true Orocodilia as existing to-day, the Belo- 

 dontia, the Aetosauria, and the Hallopoda, and all with the correspond- 

 ing portions of the more typical dinosaurs, the result may indicate in 

 some measure the relationship between them. Taking first the pelvis 

 and hind limb, as being especially characteristic, it will be seen in 



61 



Fig. 59 — Diagram of left fore limb of Hallopus victor Marsh ; seen from the left. 

 Fig. 60. — Diagram of left hind limb of same individual. Both figures are one-half natural size. 

 Fig. 61. — Left hind leg of Laosaurus ctmsors Marsh; outside view. One-sixth natural size, 

 a. astragalus : c, calcanenm; /.femur;/', fibula; il, ilium- is, ischium; p, pubis; p\ postpubis; 

 (, tibia; I, IT.T. first, fourth, and fifth digits. 



the existing alligator, as represented in fig. 57, that the pubic bone is 

 excluded from the acetabulum, articulating with the ischium only, and 

 not at all with the ilium. The calcaneum, moreover, has a posterior 

 extension. In Aetosaurus, as shown in fig. 58, the pubic bone forms 

 part of the acetabulum, as in dinosaurs and birds, and this is a note- 



