328 



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, and is not sharply defined from the sides of the symphysis. In a third mandible of 

 the same species (Plate LI II. fig. 2, I, I) the defining ridges are better marked, the trans- 

 verse convexity is less so; and this part of the symphysis is rather longer and narrower 

 than in the other two mandibles. In these respects the third mandible approaches 

 nearer to Phascolomys latifrons; but it differs, as do the other mandibles of the same 

 species as well as those of Phase, vombatus, in the larger, especially broader, incisive 

 alveoli, and in the oblique course of their upper margins from the mid line of the sym- 

 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 LIV. 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 ylatyrhinus and Phase, vombatus* . 



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 which, 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 of 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 (v) 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 LII. 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, 

 vombatus (ib. fig. 1, v)f. I may further note that in the mandibles of two individuals 

 examined since describing that of the type skull of Phascolomys 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 Notothere, with some affinities to 

 Phascolomys, 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 LIV. fig. 1) has a subquadrate 

 transverse section ; in Phase, platyrhiuus (Plate LIII. fig. 2) and Phase, vombatus (ib. 



* This latter character differentiating Phascolomys vombatus from Plmsc. latifrons is shown in figs. 3 c & 7 c 

 of plate xxxvii. torn. cit. 



t This character is shown in the figures of the mandible of the Tasmanian and Broad-fronted "Wombats in 

 plate xxxvii. of my second memoir {torn, cit.) ; but I could not then, as now, depend upon the constancy of 

 such character. 



