PROFESSOR O^VEX OX THE FOSSIL MAMMALS OF AUSTRALIA. 



187 



physis outward and backward. The fore end of the symphysis of Phase, latifrons is at 

 once recognizable by the narrower outlets of the incisive alveoli, and the more transverse 

 course of their upper border (Plate XX. fig. 1, 6-'). The lateral borders of the outlets 

 are also more nearly vertical, and do not slope backward as they descend, like those of 

 the incisive alveolar outlets in Phascolomys plafyrlu'nus and Phase, vomhatus* . 



"With the narrower alveoli associated with the more compressed form of the incisors 

 of Phase, latifrons, one may predicate of a generally narrower diastemal part of the 

 symphysis, the upper surface of Avhich, with a mesial canal towards the end and the two 

 parallel longitudinal grooves obsolete or nearly so, is better defined from the sides of 

 this part of the symphysis. In one jaw oi Phase, latifrons the defining ridges are sharp, 

 and the intervening upper surface is concave transversely to near the incisive outlets, 

 where the defining ridges subside. I may note that the anterior outlet {y) of the dental 

 canal in three mandibles of Phascolomys platyrhinus is 1 inch 4 lines, or 1 inch 5 lines 

 behind the foremost point of the symphysis (Plate XXIL fig. 2, v) : in one mandible of 

 Phase, latifrons (ib. fig. 3) it is 1 inch behind the fore end of the symphysis, in another 

 mandible it is 10 lines from the same part. The foramen is more anteriorly situated in 

 the broad-fronted or hairy-nosed species: it opens nearer to the molar series in Phase, 

 vomhatus (ib. fig. 1, r)f. I may further note that in the mandibles of two indi-s-iduals 

 examined since describing that of the type skull of Phaseolomys latifrons, the intercom- 

 municating foramen from the entry of the dental canal to the outer surface of the base 

 of the coronoid is smaller in one, as in the type mandible, than in the Platyrhine and 

 Tasmanian Wombats, while in the other it does not exist. It is interesting to find 

 this variety, because, in the great Diprotodon and Xotothere, with, some affinities to 

 Phaseolomys, the absence of the perforation of the base of the coronoid process is the 

 rule, as in the Marsupialia generally. 



The first lower molar (d 3) in Phase, latifrons (Plate XX. fig. 1) has a subquadi-ate 

 transverse section; in Phase, platyrhinus (Plate XIX. fig. 2) and Phase, vomhatus (ib. 

 fig. 1, d 3) it has an elliptic or ellipsoid transverse section. The outer depression (Plate 

 XXII.,y) of the ramus ascendens, or " ectocrotaphyte cavity," is less deep in Phase, 

 latifrons (ib. fig. 3), and shallows more gradually forward, than in the bare-nosed recent 

 species (ib. figs. 1 & 2) ; the inflected angle [a), \-iewed from below as in Plate XXIII., 

 has a broader base in proportion to its length, and is not produced so far or directly 

 backward in Phaseolomys latifrons (fig. 3) as in Phase, platyrhinus (fig. 1). 



§ 12. Mandihular characters of extinct Womhats similar in size to the recent sj)ecies. 

 — I now proceed to apply the above characters and comparisons of the mandibles of the 

 known existing kinds of Wombat in the attempt to elucidate the fossil mandibular 



* This latter character differentiating Phascohrays vomhatus from Phase, latifrons is sho\sii in figs. 3 c & 7 c 

 of plate xxxvii. torn. cit. 



t This character is sho'wn in the figures of the mandible of the Tasmanian and Broad-fronted Vombats in 

 plate xxxvii. of my second memoir {torn, cit.) ; but I could not then, as no-w, depend upon the constancy of 

 such character. 



