AND CLASSIFICATION OF THE FOSSIL REPTILIA. 
223 
A large number of South African Reptiles were separated by Sir PacnAUD Owen 
from the Anomodontia, in 1876, to form the order Theriodontia. In several genera 
the dentition is of the Carnivorous type, and the teeth were regarded as making 
approximations towards those of Mammals. The order comprised Procolophon, 
which makes a striking resemblance to Hatteria in internal structure of the skull b" 
and in simple unvarying conical form of the teeth approximates to Pareiasaurus, 
though the teeth are never serrated, and never worn down. In most of the 
Theriodont genera little is preserved of the skull beyond the characters of the snout 
and the dentition, which are well seen in Lycosaurus, Cynosuchus, Tigrisuchus, Cyno- 
draco, Cynocliampsa, and Galcsaurus. The chief character in the majority of these 
genera, which necessarily distinguishes them from Procolophon, is the development 
of a pair of tusks in the position of canine teeth. But this attribute has already 
been found to characterize the Dicynodontia, in which, however, there are no other 
teeth developed. The value of the character in classification is unknown, and 
Sir R. Owen has suggested that the toothless animals named Oudenodon may 
possibly be the females of Dicynodon. The only difference of character in these teeth 
in Theriodonts is that their margins are serrate, and that the serration extended, in 
some degree, to all the teeth. But in Paremsaurus and Anthodon the serration is 
well developed, without any indication of canine teeth; while in GalcsauruR it is 
reduced to a lateral notch or two, dividing the crown in the molar region into 
denticles. In some genera the incisor teeth are large and the molar teeth very small. 
Other characters of the order have been defined by Sir R. Owen in communications 
to the Geological Society. In a memoir on Cynodraco,\ the canine teeth are compared 
to those of Machairodus, while the toothless interval which separates the canines 
from the lower incisors is found in the Marsupial genus Didelphis. In the humerus 
of Cynodraco there is a canal crossed by a bridge of bone at some distance above the 
distal condyle, on the internal and inferior aspect of the bone. This character is 
regarded as a characteristic of the Feline family of Carnivora. A similar canal is 
found in the humerus of Seals, of Insectivora, of Edentates, and Marsupials. This 
humerus (Brit. Mus., No. 47,910) is about 27 centims. long, and on its external 
border, at about 10 centims. from the distal end, I find evidence of a second foramen, 
much smaller than that upon the opposite side, which might be easily overlooked, 
since it has not been excavated by the Museum “ masons.” It is about 6 millims. in 
diameter, and appears to pass obliquely downward through the bone. I have no 
doubt that this second foramen is homologous with the similarly placed foramen in 
the humerus of Hatteina; but, while its occurrence parallels the humerus with the 
Rhynchocephalian tj^pe, the correspondence is not less close, in this respect, with the 
Edentate Cyclothurus. Humeral bones of Dicynodor.ts are often broken in the 
slender part of the shaft in which the foramina are present ; and a fragment may 
* “ On new species of Frocolopion, &c.,” ‘ Geol. Soc. Quart, Jonrn.,’ vol. 34. 
t ‘ Geol. Soc. Quart. Jonrn.,’ vol. 32, 1870. 
