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PROFESSOR OWEN ON THE SPECIES OF PHASCOLOMYS. 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. 
§ 8. 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” (Pl. LIV. fig. 3); “the inner angle of the 
condyle” (ib. fig. 5, 6) “is less produced ; the coronoid process” (ib. fig. 3, ¢) “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 confirmed the constancy of the above characters. They likewise 
serve to differentiate the mandible of Ph. latifrons from that of Ph. platyrhinus, save 
that the coronoid process rises higher in the platyrhine species (Pl. LIV. fig. 2, ¢) than 
in the Tasmanian Wombat (ib. fig. 1, c); but the broader proportion of the process, as 
compared with that in the hairy-nosed Wombat (ib. fig. 3, ¢) 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 (Pl. LIV. fig. 5, , and Pl. LVII. 
fig. 8,4). In both the Tasmanian (Pl. LV. fig. 5, 6) and platyrhine (Pl. LIV. fig. 4, 0) 
Wombats this angle is more produced and deflected. 
The diastemal part (Pls. LIV., LV., & LVIL., J, 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 7} lines (Pl. LVII. fig. 1, s’), in the other 1 inch 63 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 (J, 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 103 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 ITI, (1845) in Trans. Zool. Soc. vol. iii. p. 304, pl. xxxvii. 
figs. 2 & 5. 
VOL. ViIL—ParT vi. May, 1873. 3E 
