VERTEBRATA 



47 



which belongs to the Permian of Europe and North 

 America. (Fig. 15). 





Fig. 15, — Cricotus heteroclitus Cope ; one-third natural size. From Permian of Texas, 

 a, head from aove ; &, part of belly f rfim below. From Cope. 



The MiCROSAURi embraces the following families : Bran- 

 chiosauridse ; Hylonomidae ; MolgophidfB ; Phlegethontiidae. 

 The smaller forms are mostly from the Coal Measures, 

 while some large ones occur in the Trias. Some of the 

 Hylonomidae come from the Permian of North America and 

 Europe. They were mostly of small size, and their verte- 

 brae exhibit very various degrees of ossification. In some 

 the bodies are completely ossified, while in others the ossi- 



