THE SUBCLASS SYNAPSIDA 233 



tidae. Permocarboniferous (Uppermost Carboniferous and Lower- 

 most Permian). 



A. Suborder Pelycosauria 



Family Sphenacodontidae (Pelycosauria). Carnivorous reptiles 

 of from four to eight feet in length, with long, often very long, dor- 

 sal spines; three sacral vertebrae. 



Sphenacodon Marsh, New Mexico. Dimetrodon Cope, Texas. 

 Clepsydrops Cope, Illinois, Texas. Tetraceratops Matthew, Texas. 

 Bathygnathus Leidy, Prince Edward Island. 



B. Suborder Edaphosauria 



Family Edaphosauridae (Edaphosauria). Subaquatic or terres- 

 trial invertebrate feeding reptiles, from six to eight feet in length. 

 Spines of dorsal vertebrae very long, each with transverse processes. 

 Skull small, short, high, with numerous palatal and coronoid conical 

 teeth. 



Edaphosaurus Cope, Texas, New Mexico. Naosaurus Cope, Texas, 

 New Mexico, Ohio, Germany, Russia. 



C. Suborder Poliosauria 



Family Poliosauridae. Lizard-like, insectivorous, four or five 

 feet in length. Teeth conical; spines of vertebrae short; two sacral 

 vertebrae. Texas and New Mexico. 



Varanops Williston, Varanosaurus Broili, Poliosaurus Case, 

 Poecilospondylus Case, Arrihasaurus Williston, Scoliomus Williston 

 and Case. 



Family Ophiacodontidae. About six feet in length, carnivorous. 

 Skull narrow; teeth slender and conical or flattened; temporal open- 

 ing small, an upper one also in Ophiacodon; ribs holocephalous; 

 limbs short and stout; two sacral vertebrae. Texas and New Mexico. 



Ophiacodon Marsh, Theropleura Cope, Diopeus Cope, Secodonto- 

 saurus WiUiston. 



D. Suborder Caseasauria 



Family Caseidae (Caseasauria) . Thickset, crawling and probably 

 burrowing, invertebrate-feeding reptiles about four feet long. Skull 



