COMPARATIVE ANATOMY. 



in the plane of the abdominal walls, become closely pressed 

 together in the middle line, and so give rise to a well-marked 

 keel (Fig. 78). 



II- 



FIG. 78. PELVIC ARCH OF FROG (Rana esculenta}. (A, from below ; B, from the 



side.) 



11, P, ilium ; Is, ischium ; Kn, pubis (?) (pars acetabularis ?) ; Cr, the median 

 ventral ischio-pubic crest ; G, acetabulum ; Oc, urostyle ; Ft, transverse process 

 of sacral vertebra. 



Fia. 79. PELVIS OF Lacerta muralis. (Ventral view.) 



11, ilium ; Is, ischium ; Fo, foramen in the pubis for the obturator nerve ; Kn, Kn 1 , 

 cartilaginous elements lying at the symphysis of the ischium (Sy) and pubis 

 respectively ; B, fibrous band connecting these cartilages ; Fc, foramen cordi- 

 forine ; t, tubercle of ilium ; G, acetabulum. 



Reptiles and Birds. In these, the well-ossified elements 

 of the pelvis are sharply differentiated, and, as the pubis in 



