6 
possess the means to investigate the nature of the doubts, and re- 
assure the confidence of geologists in their great guide. 
When Cuvier first hastily examined at Oxford, in 1818, one of 
the jaws described in this paper, and in the possession of Dr. Buck- 
land, he decided that it was allied to the Didelphys (me semblérent 
de quelque Didelphe*) ; and when doubts were raised by M. Con- 
stant Prevost, in 1824+, 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 hay- 
ing ten molars in a series in the lower jaw: (‘il [the drawing] me con- 
firme dans ]’idée que la premiére inspection m’en avoit donnée. C’est 
celle d’un petit carnassier dont les macheliéres ressemblent beaucoup 
a celles des sarigues; mais il y a dix de ces dents en série, 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 ; 
fourthly, the parts above described form one continuous portion with 
the horizontal ramus of the jaw, neither the articular condyle nor 
the coronoid being distinct pieces as in reptiles. These are the 
characters, Mr. Owen believes, on which Cuvier formed his opinion 
of the nature of the fossil; and they have arrested the attention of 
* Ossemens Foss., tome ili. p. 349. 
+ Annales des Sciences Nat., Avril, 1825; also the papers of Mr. Bro- 
derip and Dr. Fitton in the Zoological Journal, 1828, vol. ili., p. 409. 
