118 



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 fibro-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.) 



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

 foramen ; B, fibrous band between the symphyses pubis and ischii ; t, pars 

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

 pubis ; h, 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 ; /, II, first and second sacral vertebras ; 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. 96 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 



