62 Geoloylcal Society. 



the jaws described In this paper, and in the possession of Dr. Buck- 

 land, he decided that it was allied to the Didelphys (me semblerent 

 de quelque Didclphe) *; and when doubts were raised by M. Con- 

 stant Prevost, in 1824f, relative to the age of the Stonesfield slate, 

 Cuvier, from an examination of a drawing made for the express pur- 

 pose, was confirmed in his former determination ; but he added, that 

 the jaw differs from that of all known carnivorous Mammalia, in ha- 

 ving ten molars in a series in the lower jaw : (" il [the drawing] me con- 

 firme dans l'idee que la premiere inspection m'en avoit donnee. C'est 

 celle d'un petit carnassier dont les machelieres ressemblent beaucoup 

 a celles des sarigues ; mais il y a dix de ces dents en serie, nombre 

 que ne montre aucun carnassier connu." Oss. Foss. 111. 349. note.) 

 It is to be regretted that the particular data, with the exception of 

 the number of the teeth, on which Cuvier based his opinion, were not 

 detailed ; but he must have been well aware that the grounds of his 

 belief would be obvious, on an inspection of the fossil, to every com- 

 petent anatomist : it is also to be regretted that he did not assign to 

 the fossil a generic name, and thereby have prevented much of the 

 reasoning founded on the supposition that he considered it to have 

 belonged to a true Didelphys. 



Mr. Owen then proceeded to describe the structure of the jaw ; 

 and he stated that having had in his possession two specimens of the 

 Thylacotherium Prevostii belonging to Dr. Buckland, he has no hesi- 

 tation in declaring that their condition is such as to enable any ana- 

 tomist conversant with the established generalizations in compara- 

 tive osteology, to pronounce therefrom not only the class but the 

 more restricted group of animals to which they have belonged. The 

 specimens plainly reveal, first, a convex articular condyle; secondly, 

 a well-defined impression of what was once a broad, thin, high, and 

 slightly recurved, triangular, coronoid process, rising immediately 

 anterior to the condyle, having its basis extended over the whole of 

 the interspace between the condyle and the commencement of the 

 molar series, and having a vertical diameter equal to that of the ho- 

 rizontal ramus of the jaw itself : this impression also exhibits traces 

 of the ridge leading forwards from the condyle and the depression 

 above it, which characterizes the coronoid process of the zoophagous 

 marsupials ; thirdly, the angle of the jaw is continued to the same 

 extent below the condyle as the coronoid process reaches above it, 

 and its apex is continued backwards in the form of a process ; 



* Ossemens Foss., tome iii. p. 349. 



f Annales des Sciences Nat., Avril, 1825 ; also the papers of Mr. Bro- 

 derip and Dr. Fitton in the Zoological Journal, 1828, vol. iii., p. 409. 



