PKOFESSOE OWEN ON THE SPECIES OP PHASCOLOirYS. 353 



defining a longitudinal canal traversing the upper part of the nasal meatus. The pre- 

 turbinal rises from the side of the floor of the chamber. The frontal is excavated 

 by three sinuses above the rhinencephalic chamber and the hind part of the rhinal or 

 nasal one. The roof of the cranium, at the section, has a close cancellous structure 

 5 lines thick above the prosencephalon, 11 lines thick above the epencephalon. 



§ 3. Mandibular Characters of Phascolomys. 



In differentiating from cranial characters the species of Wombat called Phascolomys 

 latifrons, I noted, in comparing it with Phascolomys vombatus, that " The curve of the 

 lower border of the lower jaw is deeper" (PI. LIV. fig. 3); "the inner angle of the 

 condyle" (ib. fig. 5, b) " is less produced ; the coronoid process" (ib. fig. 3, c) " is higher 

 and narrower, and the postsymphysial depression is almost obsolete " '. With the 

 exception of the latter particular, which is variable in both species, subsequently 

 acquired skulls have confii-med the constancy of the above characters. They likewise 

 serve to diflferentiate the mandible of Ph. latifrons from that of Ph. platyrhinus, save 

 that the coronoid process rises higher in the platyrhine species (PI. LIV. fig. 2, c) than 

 in the Tasmanian Wombat (ib. fig. 1, c); but the broader proportion of the process, as 

 compared with that in the haiiy-nosed Wombat (ib. fig. 3, c) is retained. The deeper 

 curve described by the lower contour of the jaw from the neck of the condyle to the 

 incisive alveoli is a constant and well-marked character of Ph. latifrons (ib. fig. 3). So, 

 likewise, is the less-produced inner angle of the condyle (PI. LIV. fig. 5, b, and PI. LVII. 

 fig. 3, b). In both the I'asmanian (PI. LV. fig. 5, b) and platyrhine (PL LIV. fig. 4, b) 

 Wombats this angle is more produced and deflected. 



The diastemal part (Pis. LIV., LV., & LVII., I, s') of the long symphysis (ib. s, s') is 

 subject to some variety in existing Wombats. In two mandibles of Ph. platyrhinus, in 

 which the length of the series of molar alveoli is 2 inches 3 lines, that of the interval 

 between the first alveolus and the foremost angle of the symphysis is, in one skull 

 1 inch 7i lines (PL LVII. fig. 1, s'), in the other 1 inch 6| lines ; the breadth of the 

 diastema midway is the same in both, viz. 10 lines. In a mandible of Ph. latifrons 

 with the molar series of alveoli 2 inches in extent (PL LVII. fig. 3), the diastema {I, s'), 

 taken as above to the foremost point at the interspace of the incisors, is 1 inch 3 lines. 

 In a second mandible, with the molar alveoli 1 inch 10^ lines in extent, that of the 

 diastema is also 1 inch 3 lines ; the breadth of the diastema midway is, in the first 

 mandible 8 lines, in the second 7 lines. 



In the two mandibles of the platyrhine Wombat compared, the diastema is slightly 

 convex both lengthwise and across ; it is traversed by a pair of shallow longitudinal 

 grooves (ib. fig. 1), and is not sharply defined from the sides of the symphysis. In 

 a third mandible of the same species the defining ridges are better marked, the trans- 



' " On the Osteology of the Marsupialia," — Part II. (1845) in Trans. Zool. Soc. vol. iii. p. 304, pi. xxxvii. 

 figs. 2 & 5. 



VOL. viii. — PAKT VI. May, 1873. 3 e 



