148 



COMPARATIVE ANATOMY 



Amphiuma this is indicated by the fact that its anterior epipubic 

 process is paired throughout life (Fig. 107, A, B). In the 

 Derotrema and Myctodera, the anterior end of the median epi- 

 pubic process is bifurcated (c, D). 



As already indicated, the ischiopubic plate is phylogenetically 

 the oldest part of the pelvis, and various modifications as regards 

 the degree of its fusion into a median unpaired plate and of its 

 ossification occur amongst Amphibians ; the typical triradiate 

 arrangement of the pelvic bones (ilium, ischium t and pul)is\ such 



FIG. 108. PELVIS or ANURA. A, Xenopus, from below; B, the same from 

 the front ; C, Rana excit/enta, from the right side. 



Ac, acetabulum ; Cep. epipubic cartilage ; /, ilium ; 7 1 (in Xenopus), the 

 proximal end of the ilium, which is separated from its fellow and from 

 thepubis by a + -shaped zone of cartilage, f, * ; /.s, ischium ; P, pubis (7* 1 in 

 Rana, pubic end of ilium). 



as is further differentiated in certain Stegocephali and in Reptiles, 

 is already sketched out. 



One of the most characteristic differences between the pelvis 

 of Fishes and that of Amphibians is seen in the marked develop- 

 ment of the iliac region in the latter group. The ilium, like the 

 scapula, extends upwards in the lateral walls of the body ; and in 

 Proteus and Amphiuma, owing to the reduction of the limbs in 

 these forms, does not reach the vertebral column (Fig. 107, A, B). 

 In all other Amphibia, as in the Amniota, it comes into connection 

 with the sacrum, owing to the necessity for the hind-limb to act 

 as a support for the body in terrestrial animals. 



The pelvis of the Anura differs from that of Urodela in the 

 following characteristics. In correspondence with their mode of 

 progression, the ilium of each side becomes extended so as to form 



