308 THEROMORPHA CHAP. 



Direct affinity of Endotliiodon (evBoOi, within) with Placodus 

 is unlikely ; the same applies to the Dicynodontia, although 

 the restriction of the teeth to the palate seems to point us 

 much to the former genus as do the toothless cutting edges 

 of the jaws to the forms like Oudenodon. 



Other Theriodont reptiles have been described from the upper 

 Permian of Russia, for instance Deuterosaurus and Srithopus, 

 but the determination rests upon insufficient fragments. North 

 America has yielded many strange Theromorphous fossils, some 

 of which may belong to the Theriodont order, while others seem 

 to be intermediate between this and the other orders. Diadectes 

 of Texas, for instance, seems to be a Theriodont creature ; while in 

 Empedias molaris, with a skull about 8 inches in length, the 

 teeth form an uninterrupted series without distinct canine tusks, 

 and the incisors are distinguished from the molars only by the 

 transversely broadened shape of the latter. Very small teeth are 

 arranged along the median line of the vomer and united palatine 

 bones. In Clepsydrops, Dimetrodon, and Naosaurus of Texas the 

 teeth are differentiated into incisors, canines, and molars, although 

 not so regularly as in the typical Theriodont forms described 

 above, one or more pairs of teeth being enlarged into canine-like 

 tusks. In the latter two genera the spinous processes of the 

 thoracic vertebrae are enormously elongated, standing up vertically 

 to a height of 2 feet, while the centra of the vertebrae measure 

 only one inch in diameter. In Naosaurus claviger these upright 

 spines carry on either side half a dozen transverse projections. 

 Stereorhachis of the Permian of France is typically Theriodont in 

 the structure of its shoulder-girdle, humerus, and pelvis, but the 

 dentition is composed of | incisors, no canines, and T ^ pointed 

 molars. 



The following genera have been placed by Seeley in the family 

 Gomphognathidae. Microgoinphodon, with broader and less pro- 

 minently multicuspid teeth than those of the typical Theriodonts, 

 seems to lead to Go mphognathus, which has the following dentition: 

 i. , c. ^, m. ^f, with a long diasteina between the canines and 

 molars, some of which latter are nearly as broad as they are long, 

 and have comparatively low tubercles on the crowns. The skull 

 is remarkably like that of a Carnivorous Mammal. There are 

 incisive foramina behind the premaxilla. The maxillaries and 

 palatines form a united palatal roof, and behind them open the 



