AXOMODONTIA. 



401 



The following genera with In-oad molar-like teeth have been united by 

 Seeley into a special order, the Gomphodontia : 



Tritylodon Owen, with transversely expanded molar-like teeth and a 

 pair of large incisors probably growing from persistent pulps ; with a 

 secondary palate and reduced quadrate ; very mammal-like, known by 

 skull only ; molars mnltituberculate. Diademodon Seeley, Trirachodon 

 Seeley, both with multitviberculate teeth. Theriodesmus Seeley, known 

 by a remarkably mammalian fore-limb and manus ; and other genera. 

 All the above are from S. Africa. Triglyphus Fraas, known only by its 

 molar-like teeth is from the U. Trias, Stuttgart. 



The following known from imperfect remains from the Permian of 

 Russia are probably Thei-iodontia ; Deuterosaurus Eichw., Rhopalodon 

 Fischer, with lanceolate molars and sclerotic ring. 



Fig. 222. — Cynognathus crateronotus, right side of skull with imperfect mandible (after Wood- 

 ward slightly restored). The molars possibly project further than in life and the crowu 

 of the last is broken. d dentary ; j jugal ; l.t.f. small lateral temporal vacuity ; la 

 lacrymal ; mx maxilla ; na nasal ; orb orbit ; pa parietal ; pm.v premaxilla ; prf prefrontal ; 

 pto postorbital ; p</ postfrontal ; st supratemporal ; sq squamosal. 



Order 3. 13icynodontia. 



Highly specialised land-forms, known by fragments from the Trias of 

 S. Africa, East India, the Urals, and Scotland. There is a single temporal 

 arcade formed mainly by the squamosal which is very large and lies over 

 the small quadrate (Fig. 223). The jaws are edentulous except for the 

 occasional presence of a pair of tusk-like teeth in the maxillae growing from 

 persistent pulps. There do not appear to be any secondary palatal plates 

 and the pterygoids are large, meeting in front of the basisphenoid. The 

 cervical ribs are double-headed, the dorsal single-headed ; the vertebral 

 column consists of 7 to 8 cervical, 12 to 13 dorsal, 5 to 6 fused sacral and 

 about 20 caudal vertebrae. There appears to be a pineal foramen. The 

 scapula has an acromion, the pelvic bones are fused into an os innominatum. 

 i :.' Dicynodon Owen, Oudenodon Owen, Ptychognathus Owen, Karoo Sand- 

 stone of S. Africa. Gordonia and Geikia Newton, Elgin Sandstone 

 Scotland ; etc. 



