THE PECTORAL AND PELVIC GIRDLES 



145 



A small opening soon appeared where the four bones meet below 

 in the Theromorpha (Figs. 114 c, 117), and increased in size, till, in 



Fig. 118. Pelves and sacrum: A, Varanus (Lacertilia), from the right. B, Erythrosuchus 

 (Parasuchia), from the right. After Broom. One tenth natural size. C, Rutiodon (Phyto- 

 sauria), from below. After McGregor. One eighth natural size. D, Nyctosaurus (Ptero- 

 sauria), sacrum and right innominate bone from within; D', anterior parasternal ribs of 

 same ; D", prepubis of the same from below. 



Fig. 119. Pelves (Therapsida): A, Galechirns (Dromasauria). After Broom. Nearly 

 natural size. B, Diademodon (Cynodontia). After Broom. About one half natural size. 

 C, GalepHS (Dromasauria). After Broom. Nearly natural size. 



most reptiles, since Triassic times at least, this pubo-ischiatic open- 

 ing extended on each side nearly to the acetabulum, leaving only a 

 narrow connection between the pubis and ischium (Fig. 118). Later, 



