82 FOSSIL MAMMALIA OF THE 



Small as is this fragment, some useful inferences may be drawn from it. Firstly, that 

 the two molars in sifil were small, not to say minute, in relation to the entire mandible ; 

 and occupied not much greater extent — if any — of the dental scries than do the alveolar 

 indications of such molars in the former specimen (fig. 10 a). Secondly, that the line of 

 action in which they worked upon the upper molars was more vertical than horizontal ; 

 could hardly have been transverse, seeing the sheer wall by which the inner half of the 

 crown rises above the outer half. The two molars are plainly of the character of the 

 tulierculars terminating the carnassial series of flesh-feeders, adapted for pounding and 

 squeezing out the juice of imperfectly divided animal tissues; not fitted, for the rotatory 

 grinding actions by which vegetable substances are reduced, with salivary admixture, to 

 a pulp ; but taking that share in the dividing work which the larger of the two small 

 mandibular molars does in Thylacoleo carnifcx. 



Plaoiaulax Becklesii, Falconer. Plate IV, figs. Via, a, 13^, b. 



This species is, again, represented by the fore part of the I'ight mandibular ramus witli 

 the implanted base of the broken incisor («), part of the first {p 2), the second {p 3), and 

 the fore part of the third {p 4) premolars. The inner side of the specimen is represented 

 in PL IV, fig. 13, nat. size, 13 b, magn. three diam. : the outer side of the specimen is 

 represented in fig. 13«, nat. size, 13 a, magn. three diam. In both figures the parts 

 wanting, but preserved in the preceding specimens, are restored in outline. 



The symphysial surface (fig. 13 b, s, r), extends upward and forward at an angle of 

 147° with the lower line of the mandible (r, a). It is indented behind, the part (.s) abovf 

 the entering notch suddenly expanding. A linear groove extends from the notch forward 

 across the symphysial surface, dividing the upper broad from the lower narrower part of 

 the articular surface. The inner surface of the ramus is slightly swollen behind the upper 

 part of the symphysis by the corresponding wall of the long socket of the laniarifonn ft-ont 

 tooth («), and the vertical convexity of that swelling changes to a concavity as the inner 

 surface descends to the thick rounded lower margin. 



The crown of the second premolar [p 3) swells out on the inner side (fig. 13 a) above 

 the roots, with a concavity or notch, which divides the swollen base into two smooth pro- 

 tuberances, the anterior being the most prominent. Above this the inner surface is flat to 

 the trenchant margin, not defining a cingnlum. The flat inner surface of 7; 3 is traversed 

 by four linear ridges extending from above downward and forward, each ridge being 

 continued from the summit of the low projection, the succession of which gives a fine 

 serrate character to the trenchant bonier of the tooth. 



The ramus has been fractured across the third premolar {p 4), showing the length of 

 the implanted fang (fig. 13 b) ; the degree of outswelling of the base of the crown both 



