94 



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 



A B 



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



side. ) 



II, P, ilium ; 7.9, ischium ; Kn, pubis (?) (pars acetabularis ?) ; Cr, the median 

 ventral ischio-pubic crest ; G, acetabuluin ; Oc, urostyle ; Pt, transverse process 

 of sacral vertebra. 



FIG. 79. PELVIS OF Laecrta mural ix. (Ventral view.) 



Jl, ilium ; 7s, isc-hium ; Fo, foramen in the pubis for the obturator nerve ; Kn, AV, 

 eartila<jinous elements lying at the symphysis of the iscliiiim (.V//) and pubis 

 respectively; 7>, iilirous band connecting these cartilages ; Fc, foramen cordi- 

 fonne ; 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 



