244 REMARKS ON POST-TERTIARY PHASCOLOMYID^E, 



average jaw of mitchelli it is 51 ; the width of m 3 is 6*8 mm., 

 against 7*8 in mitchelli, the difference of a millimetre throughout 

 the series asserting itself plainly to the eye. The premolar is 

 unusually large and unusually rectilinear in form ; the midline of 

 its flat inner side is sharply impressed with a vertical groove, and 

 its longitudinal axis is all but coincident with the longitudinal 

 axis of the alveolar series. The lobes of m 1 are as usual nearly 

 at right angles to the line of teeth, those of m 2 are distinctly 

 oblique, of m 3 more so, and of m 4 still more so. The lower 

 contour of the jaw is flatly arched, being rather the deepest in the 

 middle and not less deep beneath p 4 than under m 4 — it approaches 

 that of platyrhimis and differs much from that of mitchelli. The 

 coronoid process is, at its base, more than usually exserted from the 

 side of the jaw, is thick and massive, and has on its anterior edge 

 a peculiar character, a series of short, strong, oblique ridges. The 

 symphysis in this mandible extends only to the middle of m l , but 

 its condition shows that anchylosis with its fellow had hardly 

 begun, and that, consequently, its shortness is attributable to its 

 youth, notwithstanding that m 4 is worn down to smooth surfaces. 

 The depth of the jaw opposite m 1 is 38, that of P. platyrhinus 

 being 32-5. 



The associated limb is but a fragment with the four true 

 molars in place and affords no further information. The third 

 example is a right dentary limb, containing m 1 , m 2 , m 3 , and half 

 of m 4 , the teeth being equally narrow and oblique posteriorly. 

 The symphysis in this example extends to the hinder lobe of m 2 . 

 The fourth subject is similar to the last, but contains only m 1 , 

 m 2 , and m 3 . The symphysis is indistinct, but appears to have 

 extended to the fore lobe of m 1 . The teeth are similar in width 

 and obliquity. 



Fortunately the existence of this species is affirmed by other 

 than mandibular testimony. Inferring from the narrowness of 

 its teeth that angustidens, though equal in size to mitchelli, was 

 more delicate in structure, I refer to it a nearly perfect humerus 

 and a tibia which convey the same impression. The humerus differs 

 generally from that of mitchelli in its comparative slenderness, and, 



