THE ENDOSKELETOX 



705 



The elasmobranchs have a true girdle, although there are no sepa- 

 rate elements in it, and it does not ossify, there being but a continuous 

 ischiopubic bar running from one acetabulum to the other, with an 

 elongated iliac process running dorsad. 



The pelvic girdle lies free of the vertebral column in all fishes, but 



isc.pu. 



Fig. 419. 



A The skeleton of the pelvic fins and B. The pelvic girdle of a rabbit, 



girdle of a female dogfish. from beneath. 



ac., Acetabular surface ; bp., basiptery- 

 gium ; h.r., horny rays ; tZ., iliac process ; 

 isc.pu., ischio-pubic region ; rad., cartilagi- 

 nous rays. 



ac., Acetabulum ; tt., ilium ; is., 

 ischium ; ob.f., obturator foramen ; 

 pu., pubis ; sym., symphisis pubis. 

 (From Borradaile). 



Isdi 



C. 



C. Anlage of pelvic girdle of 6-day 

 chick embryo to show develop- 

 ment. 



II, ileum ; Isch., ischium ; pb., 



pubis ; pp., pectineal process. (After *+ 



Johnsohn). 



in animals that have to support the body-weight upon their limbs, the 

 pelvic girdle becomes definitely attached to the sacrum by the develop- 

 ment of one or more sacral ribs. 



In the mud puppy (Necturus, Fig. 375), the median cartilage extends 

 forward as an epipubic process, while from the antero-lateral portion of 

 each pubic bone or cartilage, a pectineal process extends, and, in the 

 salamanders, to the extent of two or three somites, there is a cartilage 



