PURBECK FORMATIONS. 71 



fossil, the part of a right mandibular ramus was exposed, which is represented, of the 

 natural size, in PI. IV, figure 3. 



The preserved molar {m 2) is of the Triconodont type ; but the size of the specimen is 

 fully one third larger than the largest of the previously described species of Triconodon. 

 The animal to which it belonged would probably be of the size of the ' Native Cat ' of 

 Australia {Dasyurus Mavgei, Geoffroy). I estimate the length of the lower jaw of Tricono- 

 don. major, when entire, according to the analogy of Triconodon ferox (PI. Ill, fio-s. 7 and 

 8), to have been two inches and a half, and the jaw attains that length in the male of the 

 spotted species of Dasyure above cited. 



The tooth preserved, which lacks only the apex of the anterior cone, answers to the 

 second of the three molars in Tr. ferox (PL III, fig. 12). It shows the usual absence of 

 continuous cingulum along the outer side of the base of the crown. There is no trace of 

 anterior or posterior talon. The coronal clefts seem to be rather less deep than in the 

 smaller species. The socket and remnant of the first molar shows it to have been, as in 

 Tr. ferox, smaller in proportion to the second molar than it is in Tr. mordax. The last 

 premolar (jo 4) shows the same relative antero-posterior extent of crown as in the smaller 

 species : the two fangs supporting the base of the crown are partially exposed, but the rest 

 of the tooth is broken off. The socket for the two fangs of the penultimate premolar {p 3) 

 is preserved, anterior to which the jaw is broken ofi", exposing the anterior root of that 

 tooth and the cavity of the ramus (fig. 3 a). 



The two-celled socket of the molar following the one in place indicates a tooth of equal 

 size ; and the position of the outer buttress-like beginning of the fore part of the coronoid 

 process shows m 3 to have been the last. The stone-saw has removed an extent of two 

 lines between the beginning of the coronoid and the rest of the rising branch. This o-ives 

 a basal fore-and-aft breadth of the coronoid of eight lines ; the apex or upper half of the 

 process is wanting. A similar notch between the hind border of the process and the 

 condyle, as in PI. Ill, figs. 6 and 10, gives the same pedunculate character to the upper 

 part of the condyle ; the joint projects at a lower level than the alveolar outlets. From 

 its lower end a ridge (a) projects outward, but in a less degree than in Dasyurus, definint^ 

 below the crotaphyte fossa. 



The fractured fore part of the jaw exposes the anterior cell or division of the socket of 

 the third premolar, filled with matrix, and the cavity of the ramus itself similarly 

 occupied. The bone has suffered a longitudinal fracture towards its hind part. 



