Geological Society, 63 



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 

 M. Valenciennes in his endeavours to dissipate the doubts of M. de 

 Blainville*. 



From the examination of a cast, the latter, however, has been in- 

 duced to infer that there is no trace of a convex condyle, but in 

 place thereof an articular fissure, somewhat as in the jaws of fishes; 

 that the teeth, instead of being imbedded in sockets, have their fangs 

 confluent with or anchylosed to the substance of the jaws, and that 

 the jaw itself presents evident traces of the composite structure. 



In answer to the first of these positions, Mr. Owen states that the 

 portion of the true condyle which remains in both the specimens of 

 Thylacotherium examined by Cuvier and M. Valenciennes, clearly 

 shows that the condyle was convex, and not concave. It is situated 

 a little above the level of the grinding surface of the teeth, and pro- 

 jects beyond the vertical line, dropped from the extremity of the coro- 

 noid process, but not to the same extent as in the true Didelphys. 

 In the specimen examined by M. Valenciennes, the condyle corre- 

 sponds in position with that of the jaw of the Dasyurus rather than 

 the Didelphys ; it is convex, as in mammiferous animals, and not 

 concave as in oviparous. The entire convex condyle exists in the 

 specimen belonging to the other genus, Phascolotherium, now in 

 the British Museum, but formerly in the cabinet of Mr. Broderip. 

 Mr. Owen is of opinion that the entering angle or notch, either above 

 or below the true articular condyle, has been mistaken for " une 

 sorte d'echancrure articulaire, un peu comme dans les poissons." 



The specimen of the half-jaw of the Thylacothere examined by 

 M. Valenciennes, like that [the drawing oi}'] which was trans- 

 mitted to Cuvier, presents the inner surface to the observer, and ex- 

 hibits both the orifice of the dental canal and the symphysis in a per- 

 fect state. The foramen in the fossil is situated relatively more for- 

 ward than in the recent Opossum and Dasyure, or in the Placental 

 Insectivora, but has the same place as in the marsupial genus Hypsi- 

 prymnus. The symphysis is long and narrow, and is continued for- 

 ward in the same line with the gently convex inferior margin of the 

 jaw, which thus tapers gradually to a pointed anterior extremity, 



* Coraptes Rendus, 1838; Second Semestre, No. 11, Sept. 10, p. 527 

 et seq. 



