174 MR. D. M. S. WATSON ON 



Super-Family Ophiacodontid^. 



Pelycosaurs with a curved tooth-row and slightly differentiated 

 dentition. A small supra temporal. Stapes articulating with 

 the edges of the fenestra ovale and by a special head with the 

 under surface of the paroccipital process. Cervical neural arches 

 not heavy. 



Deiojjeus Cope. Artinskian, Texas. 



Theropleura Cope. ,, ,, 



Ophiacodon Marsh. U. Coal Measui-es, New Mexico. 



? Stereorachis Gaudry. L. Permian, France. 



Super-Family Sphenacodontid^. 



Pelycosaars with a curved tooth-row and well-differentiated 

 dentition. 



Stapes of two parts, a small element articulating with the 

 fenestra ovale and distally with a large element which articulates 

 with the paroccipital process, the pterygoid and quadrate. A 

 typical compressed and notched angular. 



Family CLEPSYDROPiDiE Cope. 



Sjihenacodontidae with a carnivorous dentition and a pro- 

 nounced step between the dentigerous edges of the premaxilla 

 and maxilla. 



Clepsydrops Cope. Artinskian, Texas. 



Upper Coal Measures, Illinois. 



Dimeirodon Cope. Artinskian, Texas. 



Sphenacodoa Marsh. „ New Mexico. 



Tetraceratops Matthew. ,, Texas. 



'^ " Geosaurus cynodics " Gervais. L. Permian, France. 



Family Edaphosaurid^ Cope. 



Sphenacodontidae with a powerful palatal dentition of small 

 teeth. 



Edaphosaiirus Cope. U. Coal Measures and L. Permian, Texas, 

 New Mexico, Bohemia, Saxony, Urals. 

 Naosaurus Cope. L. Permian, Texas. 



Super- Family Bolosaurid^. 



Systematic position very doubtful, but as the occiput seems tO' 

 be of Anomodont type and the lower jaw is undoubtedly com- 

 pressed and the angular apparently notched, they may be placed 

 here. 



Skull with large orbits and very short pre-orbital and temporal 

 region, upper surface passing smoothly into the occiput. Tem- 

 poral vacuity entirely on the side of skull and placed low down. 



