448 



surface of this part of the mandible ; is not so deep, relatively, as in Protemnodon Anak 

 The root of the incisor exposed by fracture of the symphysial part of the jaw is solid, 

 but shows no coat of enamel. The vertical diameter of the tooth is G-j lines ; the 

 transverse diameter is 4 lines ; but these, with the shape and relative position to the 

 symphysis, are shown in Plate LXXXVI. fig. 4. 



The last molar is well in advance of the coronoid plate in the present old jaw. It 

 must have belonged to a fine animal, but the superiority of size of Protemnodon Boechus 

 (Plate LXXXVII. figs. 10-13) is well marked ; the first four teeth there figured almost 

 equal in extent the entire molar series in Protemnodon Mimas. 



§ 18. Protemnodon A?itceus, Ow. — A large portion of a left mandibular ramus with 

 the molar dentition (Plate CX. figs. 1-4) of a Protemnodon agrees with Protemnodon 

 Anak in the absence of the postbasal ridge (ib. fig. 4), but differs in size, the molar series 

 extending along 3 inches 1 line (80 millims.) as against 2 inches 8 lines (68 millims.) 

 (Plate LXXXV. figs. 7, 8, 9). The extent of the molar series in the present specimen 

 is the same as in Protemnodon Mimas (Plate LXXXVI. figs. 1, 2, 3); but the propor- 

 tions of the teeth differ. The bilophodont molars in Protemnodon Mimas have a greater 

 longitudinal (fore-and-aft) extent, but the superiority in this dimension of the premolar 

 in Protemnodon Anta?us makes up for the deficiency. Add to this character the absence, 

 in Protemnodon Antceus, of the postbasal ridge, which, though narrow, is clearly shown 

 in the last three molars of Protemnodon Mimas (ib. fig. 3, m i, m 2, m 3, g). 



The superiority of size of Protemnodon Rcechiis is such as at once to forbid a reference 

 to that species of the present specimen, which shows by its dentition that it was from 

 an animal as advanced in age as that which afforded the type-specimen (Plate LXXXVII. 

 figs. 10-13) of the hugest of this genus of extinct Wallabies which has yet reached me. 



I have no alternative, therefore, than to symbolize the observed distinctive characters 

 in the mandibular fossil under review by the binomial term which heads the present 

 subsection. 



The outer side of the crown of the premolar (Plate CX. fig. 1, p 3) is obliquely and 

 smoothly worn along its upper and hinder part, in advance of which the triangular fore 

 lobe stands out ; on the inner side (ib. fig. 2, p 3) a few feeble longitudinal indents mark 

 the hollow between the fore and hind prominences ; on the summit of the latter a speck 

 of dentine is exposed (ib. fig. 3). The lidged summit of the fore lobe of m 3 shows 

 masticatory wear ; the hind lobe of this tooth stands up clear of the coronoid plate 

 (ib. ib. q). The outer alveolar ' bead ' is indicated by a linear groove, and below this 

 the wider longitudinal channel extends from beneath the premolar to the penultimate 

 molar. The diastemal ridge (ib. ib. I) curves gently forward, without the abrupt descent 

 as in Protemnodon Anak (Plate LXXXV. fig. 8, /) ; in this feature the present species 

 more resembles Protemnodon Mimas (Plate LXXXVI. fig. 1). The outlet of the dental 

 canal (Plate CX. fig. 1, v) is nearer the premolar than in Protemnodon Og (Plate LXXXV. 

 fig. 5). The elliptical section of the socket of the incisor (ib. fig. 5) gives 6 lines by 4 

 lines in its two diameters, but the fang has begun to contract at this part. The direction 

 of the incisor was more that in Macropus than in Sthenurus. 



