PB0F. OWEN ON A CARNIVOROUS REPTILE. 99 



long upper tusks in exemplifying Mammalian characters, not Lacer- 

 tian ones. The same concurrence, not only with well-defined 

 canines, but likewise with equally well-defined incisors and molars, 

 has been observed by me in several species of extinct Eeptilia from 

 the Karoo deposits of South Africa. 



The earliest examples ( Galesaurus, Cynochampsa) of such Eeptilia 

 were made known through this Society by its c Quarterly Journal,' 

 vol. xvi. (for the year 1859-60). Since that date I have had evi- 

 dences of the genera Lycosaurus, Tigrisuchus, Cynosuchus, Nytho- 

 saurus, Scalojjosaurus, Procolojplwn, Gorgonojos, as well as of the genus 

 Cynodraco, of one species of which the dental and humeral charac- 

 ters have supplied the chief subject of the present communication. 



Most of the genera above mentioned are represented by more than 

 one species * : and both genera and species are classifiable in groups 

 characterized by modifications of the structure of the external bony 

 nostrils — as, for example, into the " tectinarial," " binarial," and 

 "mononarial" families, the skull in the latter presenting, in the 

 aspect and position of the single terminal nostril, a strikingly mam- 

 malian facies. Por the name of these extinct carnivorous Saurians 

 I find it convenient, and believe it will be generally acceptable, to 

 form a distinct order of Eeptilia under the denomination of Therio- 

 dontia, with the following characters : — " Dentition of the carnivo- 

 rous type ; incisors defined by position and divided from the molars 

 by a large laniariform canine on each side of both upper and lower 

 jaws, the lower canine crossing in front of the upper; no ectoptery- 

 goids ; humerus with an entepicondylar foramen ; digital formula of 

 fore foot 2, 3, 3,^ 3, 3 phalanges." 



"When we contrast the grand development and notable modifica- 

 tions of the extinct species of Eeptilia with the poor scanty evidences 

 of the class still lingering on in life, we seem to be witnessing a 

 course of degeneration, of retrogradation, rather than of organic 

 progression in the course of time. 



Although there be none now, there have been Saurians in which 

 the articular surfaces of certain vertebrae in the same column were 

 modified — as, e. g., of the anterior ones in great herbivorous Dino- 

 saurs, for freer movements of the head, by means of an anterior ball 

 playing in a posterior cup, such as we now find in the Ehinoceros 

 and some other large mammalian herbivores. In another part of 

 the same vertebral column of these extinct reptiles we find a sacrum 

 not limited to two, but composed of five or six ankylosed vertebra?, 

 also as in these and many other mammals. 



Again, some of these vegetarian Dinosaurs had masticatory teeth 

 of a complex structure f unknown in existing phytophagous Sauria, 

 but resembling those teeth of certain phytophagous mammals, e. g. 

 Megatherium t, Mylodon §. With the modification of a portion of the 



* These will be characterized and the characters illustrated in the Plates cf 

 the Catalogue of South-African Eeptilia, on which I am now engaged by 

 direction of the Trustees of the British Museum. 



t ' Odontography,' p. 250, pi. 71 : 4to, 1840. 



\ Ibid. pi. 84. % Ibid. pi. 70. 



