PELVIC ARCH 



111 



it is perforated by nerves, and gives rise on either side to an iliac 

 process (most marked in Holocephali) extending into the lateral 

 walls of the body (Fig. 88). 



In all the above 

 cases we may look pp 



upon the pelvic plate 

 as essentially corres- 

 ponding, more or less 

 completely, with the 

 ischio-pvMs of higher 

 forms. 



Dipnoi. The 



small cartilaginous 

 pelvic plate (Fig. 89) 

 is provided with a 

 long and delicate an- 



Rad;- 



FIG. 88. DIAGRAM OF THE ELASMOBRANCH PELVIS. 



, 



S P' regi n f the ischi P ubic symphysis ; Fo\ 

 obturator foramen ; JBas, Pro, Rad, basiptery- 

 gium, propterygium, and radii of the fin. 



(From the ventral side.) 



terior median, a short BP, Pelvic plate (ischio-pubis) ; 7, iliac process ; 

 posterior median, and PP> prepubic process ; Cep, epipubic process , 



two mi- of latpral 

 01 lateral 



processes. Of the 



latter the anterior 



(prepubic processes) vary much in form and length, being much 



longer in Protopterus than in Ceratodus, and each is embedded 



in an intermuscular septum ; 

 with the posterior the skeleton 

 of the free fin is articulated by 

 means of an intermediate piece. 

 The anterior unpaired process 

 must be looked upon as an 

 epipubic process, corresponding 

 w ith that of Amphibians, Rep- 

 tiles, and Mammals (pp. 113, 

 115, 121). 



Amphibia. Urodela. It 

 will be seen by a glance at 

 Fig. 87, D, that the ventral 

 portion of the pelvic arch of 

 Necturus is formed on the same 

 plan as the pelvic plate of the 

 Dipnoi and Crossopterygii, but, 



^ Tr , ^ as in all Urodela and Amniota, 



.biG. 89. PELVIS or Protopterus. (From , f > > ,, , 



the ventral side.) ^ 1S perforated by the obturator 



. . nerve : this indicates a further 



a, prepubic process, which may become i 4.^,^1 4. T -i J.T 



forked at its distal end; b, process la ^ / S Jf"f WL 1 Llke the 

 to which the hinder extremity pelvis OI all Vertebrates, it has 



(HE) is attached ; Gr, sharp ridge, a paired origin, and in Proteus 

 wffl&7t&25f; and Amphinma this is indi- 

 M 1 , M\ intermuscular septa. cated by the fact that its- 



