PELVIC ARCH. 



93 



vertebra?, and corresponds to the iliac process mentioned above 

 as being present in some Fishes; of the latter, the anterior ventral 

 element is spoken of as the pubis, the posterior as the ischium. 

 The articular cavity for the thigh-bone (acetabulum) is situated at 

 the point of junction of the pelvic elements. Thus we meet here 

 with a ground-form essentially similar to that of the pectoral arch 

 (Fig. 71). 



In the pelvis of Urodela and Anura a single ventral plate is 

 seen on each side, which comes into contact with its fellow to form 



FIG. 77. PELVIS OF SALAMANDEE (Salamandra maculosa). (Ventral view. ) 



II, ilium ; Is, ischium ; P, pubis (?) (pars acetabularis ?) ; Fo, obturator foramen ; Sy, 

 ischio-pubic symphysis ; t, two protuberances, present in many Urodeles ; Ep, 

 epipubic cartilage, with its forked ends (a, b] ; G, acetabulum. 



a symphysis (Fig. 77, Si/}, and the anterior part of which usually 

 remains cartilaginous throughout life. It cannot, at present, be 

 stated with certainty whether this part corresponds to the pubis, 

 or to a fourth element, the pars acetabularis (Fig. 77, P, and 

 78, AV),which is present in many Amniota, inserted between the 

 pubis and the acetabulum (comp. Fig. 83 A). The posterior part, 

 which always becomes ossified, is without doubt an ischium (Is). 

 In some Urodeles a delicate rod of cartilage arises from the middle 

 line of the anterior border of the pelvis, and becomes bifurcated 

 distally (Fig. 77, Ep, a, b"). Amongst the Anura, this epipubis 

 (" ypsiloid cartilage") is only present in Dactylethra capensis, 

 where its form is somewhat different, reminding one of the delicate 

 median process of the pelvis of Dipnoi (Fig. 76, c). The so-called 

 " marsupial bones " of Monotremes and Marsupials have probably 

 been developed from the representative of the epipubis. 



In correspondence with the mode of progression in Anura, 

 the ilium of each side becomes extended so as to form a long rod 



Q 



(Fig. 78, //), and the two ventral plates, which in Urodeles lie 



