THE SACRUM OF THE LACERTILIA. 



87 



very short. They arise broadly from the centra of the vertebrse. 

 The same may be said of the adult specimen. In the Phrynosoma 

 specimens a nearer approach to the ancestral condition of the 

 vertebrate sacrum is seen. Gegenbaur (13) is of the opinion that 

 the sacrum of the vertebrates was primitively of but one vertebra 



Fig. 1. Skeleton of Phrynosoma douglassi hernandesi. Girard. 



as is found in the modern amphibians. Such a condition is what 

 would be expected. In Phrynosoma the first sacral vertebra 

 bears large stout transverse processes with expanded ends. The 

 second sacral bears, much smaller processes but they are still 

 larger than the processes on the succeeding pygals. These like- 



