174 



MR. D. M. S. WATSON ON 



Super-Family Ophiacodontid,e. 



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. 



Deiopeus Cope. Artinskian, Texas. 



Theropleura Cope. ,, 

 Ophiacodon Marsh. U. Coal Measures, New Mexico. 

 ? Stereorachis Gaudry. L. Permian, France. 



Super-Family Sphenacodontid^e. 



Pelycosaurs 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 

 typieal compressed and notched angular. 



• Family Clepsydropid^e Cope. 



Sphenacodontidse 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. 

 Dimetrodon Cope. Artinskian, Texas. 

 Sp>henacodon Marsh. ,, New Mexico. 

 Tetraceratops Matthew. ,, Texas. 

 '( " Geosaurus ci/nodus" Gervais. L. Permian, France. 



Family Edaphosaurice Cope. 



Sphenacodontidse with a powerful palatal dentition of small 

 teeth. 



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



New Mexico, Bohemia, Saxony, Urals. 

 Naosaurus Cope. L. Permian, Texas. 



Super- Family BoLOSAURiDiE. 



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. 



