PR0C0L0PH0N FROM THE CAPE COLONY. 



805 



tamed in a groove with sockets scarcely better indicated than among 

 Ichthyosanrs. 



Fig. 1. — View of Lower Jaw of a Crocodile, from above, showing ilie 

 formula I. 3, C. 1, Pm. 6, M. 9. 



Fig. 2. — Lateral View of the same Jaw, showing how these Regions 

 are indicated by Curves. 



Nor are Crocodiles the only animals in which this sort of dental cha- 

 racter is met with ; for it may be detected more or less well marked, 

 though with different divisions, in certain Plesiosaurians, some of the 

 Ornithosanria, and Teleosaurs *. It is true that no other types, of 

 reptilian affinities, have the canines so much developed as in the so- 

 called Theriodonts of South Africa ; but when we remember the 

 wide range of variation in dental characters that exists among 

 marsupial mammals, coupled with the variation of size in the 

 canines of Carnivora, there seems to be a prima facie objection to 

 the institution of an ordinal group for reptiles with canine teeth, 

 even though they may sometimes be as well developed as in 

 Machairodus. If the order is well founded, it will show cranial 

 and other characters which are more important. The South- African 

 genera classed as Theriodont by Prof. Owen are largely founded on 

 snouts, which give no indication of the structures of the skull which 

 are useful in comparison : among such genera are Tigrisuchus, 

 Cynodraco, Cynochampsa, Cynosuchus. The genera founded on 

 more or less useful crania are : — Lycosaurus, which is too imperfect 

 for comparison ; Procolophon and Scaloposaurus, neither of which 

 fall within the definition of Theriodonts, since they have no canine 

 teeth ; and, lastly, Galesaurus and Gorgonops, genera which differ 

 a good deal, of which the former shows the limits of the bones 

 on the upper surface of the skull, and the latter gives imperfect 

 indications of the structure of the palate (which, though figured, 

 has not been described). These palatal structures are similar to 

 those figured in Ptychognathus boopis, and appear to be such as 



* Continental naturalists have long used the mammalian formula for teeth 

 in describing Teleosauria (see Pictet, ' Trait6 de Paleontologie,' vol. i. p. 484, 

 et seq.). • 



