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COMPARATIVE ANATOMY 



The pelvis of the typical Lacertilia (Fig. 95 B) is characterised by 

 a lightness of build. The rod-like pubis and ischium are separated 

 from one another by large ischiopubic foramina, and between them 

 in the middle line is a longitudinal fibre-cartilaginous ligament, 

 continuous anteriorly with the plug-like epipubic cartilage and 

 posteriorly with the hypoischium. This tract represents the 



FIG. 96. PELVIS OF A YOUNG Alligator Indus. (A, ventral, and B, side view.) 



If, ilium ; Is, ischium ; P, pubis ; Sy, symphysis of ischium ; F, ischio-pubic 

 foramen ; JB, fibrous band between the symphyses pubis and ischii ; f, pars 

 acetabularis, which is interposed between the process a of the ilium and the 

 pubis ; 6, foramen in the acetabulum, bounded posteriorly by the two pro- 

 cesses, a and b, of the ilium and ischium respectively ; *, indication of a 

 forward growth of the ilium, such as is met with in Dinosaurians and Birds ; 

 G, acetabulum ; 7, II, first and second sacral vertebrae ; M, fibrous mem- 

 brane extending between the ant rior margin of the pubis and the last pair 

 of "abdominal ribs" (BR.) 



remnant of the median ends of the pubis and ischium which 

 are present in the embryo (Fig. 95 A) ; and thus in this, as in 

 certain other respects, the pelvis of the Lacertilia may be said to 

 pass through a Hatteria-like stage in the course of development. 

 The epipubis and hypoischium arise as paired rudiments. The 

 ilium in some cases is almost vertical in position : in others it is 



