No. 377.] THE ORIGIN OF THE MAMMALIA, 319 
closely united in skeletal characters as they are dissimilar in 
dental characters. These are: 
1. Suborder Cynodontia: Carnivorous animals, with cutting 
triconodont molars. 
2. Suborder Gomphodontia: Herbivorous animals, with tri- 
turating, low-crowned, tritubercular and multitubercular teeth. 
The teeth of these animals are even more widely differentiated 
than those of the Mesonychidz and Arctocyonide among the 
Creodonta. Compared with living types, they are as wide apart 
as those of Thylacinus and Mus. Upon the “ tritubercular 
theory’ the dentition of the cynodonts is the most primitive. 
Upon the “ multitubercular theory ” it would be considered the 
most specialized. 
The skeleton of the Cynodontia is by far the best known. 
1. The Cynodontia. 
The most perfectly known type is Cynognathus. The skull 
of Cynognathus is over a foot (1534 inches) long. This ani- 
mal was a large and powerful carnivore, the tooth structure 
— Lateral view of skull of C. apai Gr aterenmiis, showing ga erai A in 
the mandible ; the incipient angle — 
infratemporal fossa, ia. (3 ‘caters size. After Seeley.) 
superficially resembling that of Thylacinus or Dissacus. The 
skull widens posteriorly, but in lateral view it is strikingly 
mammalian and cynoid (1895, 5, p. 61). The anterior nares 
are divided, terminal and lateral, the snout as seen from above 
