240 THE OSTEOLOGY OF THE REPTILES 



rounding, parietal foramen. An interparietal and small tabulars. 

 Premaxillae fused and always toothless, and in life covered with 

 horny beak. Maxilla usually with an enlarged, permanently growing 

 canine, which, however, is absent in the females of some genera, and 

 generally with a number of small molars often irregularly arranged 

 in more than one series. Molars are always present on the mandible 

 if in the maxilla, but there is never any canine present. Prevomers 

 fused. A rudimentary false palate, no teeth on palatal bones. 

 Stapes large. Occipital condyle tripartite. Dentary, angular, and 

 surangular large; no coronoid. A mandibular foramen. Sclerotic 

 plates in orbits. Vertebrae amphicoelous; no intercentra back of 

 atlas; four to seven sacrals. No parasternals. Legs short and stout, 

 hands and feet short; an entepicondylar foramen. Phalangeal for- 

 mula 2,3,3,3,3. A thyroid foramen in pelvis; ilium projecting in 

 front of acetabulum. An ossified sternum. The shoulder girdle has 

 the coracoid and precoracoid well developed, and a distinct but short 

 acromion. There is a small cleithrum known in Dicynodon and 

 Cistecephalus, and possibly present in most other genera. 



Family Dicynodontidae. Middle Permian. Dicynodon Owen,. 

 Pristerodon Huxley, South Africa. 



Upper Permian. Tropidostoma Seeley, Diaelurodon Broom, Pro- 

 dicynodon Broom, Eocy clops Broom, Emydops Broom, Diictodon 

 Broom, Emydorhynchus Broom, Emyduranus Broom, Taognathus 

 Broom, Cryptocynodon Seeley, Endothiodon Owen, Cistecephalus 

 Owen, Chelyrhynchus Haughton, South Africa, Dicynodon Owen,. 

 South Africa and Russia. 



Lower and Middle Triassic. Dicynodon Owen, Lystrosaurus Cope^ 

 Prolystrosaurus Haughton, Myosaurus Haughton, South Africa. 



Upper Triassic. Kannemeyeria Seeley, Gordonia Newton, Geikia 

 Newton, Scotland. Placerias Lucas, Brachyhrachium Williston, 

 Wyoming. 



D. Suborder Theriodontia 



Carnivorous Therapsida with more or less differentiated dentition, 

 including at least one pair of upper caniniform teeth; a prominent 

 coronoid. Vertebrae never notochordal; few or no teeth on palate 

 bones. No cleithrum. Manus and pes, so far as known, rarely 

 primitive. 



