427 



molars in situ, of an older Sthenurus Brehus gives the molar (to 3) with the apical ridges 

 obliquely worn at their fore surface, but not through the enamel. It permits a com- 

 parison with the homologous tooth in the type specimen (Plate LXXXVII. figs. 5 & 6, 

 m 3), has been added to the figures 5, 7 (Plate LXXXVIIL), and completes the con- 

 firmation of the dental characters of the species. 



§ 9. Genus Protemnodon*, Ow. — The genus Protemnodon is allied to Sthenurus, but 

 distinguished therefrom chiefly by the more simple trenchant shape of the crown of the 

 premolar. 



Having ascertained the characters of that tooth in the upper jaw of Sthenurus Atlas, 

 in the specimen from the lacustrine deposits of South Australia (Plate LXXXIV. figs. 4, 

 5, 6), I subjected to a reexamination the fossil upper jaw brought to me in 1842 by Count 

 Stezelecki from the Breccia-cave of Wellington Valley, and the specimen transmitted in 

 the following year from the bed of the Condamine by Col. Sir Thomas L. Mitchell, C.B., 

 both of which specimens, from the size of the germ of the premolar (Plate LXXXIll. 

 figs. 6 & 9), had been referred, in my ' Catalogue of the Fossil Mammalia in the Royal 

 College of Surgeons,' to Macropus Atlas f. 



I had fortunately begun the quest of this tooth from the inner side of the formative 

 alveolus, and was now able to recognize, in the absence of the inner ridge or lobe 

 characteristic of the upper premolar of Sthenurus, and giving the crown of that tooth a 

 breadth corresponding with the lower premolar, that the fossils Nos. 1513, 1519 must 

 belong to another species, and, according to the estimate of the value of premolar 

 modifications, to another subgenus of Macropodidce. 



The subsequent acquisition of mandibular fossils, with the premolar simple and 

 trenchant, and with equivalent modifications of the form of the bone, have afforded the 

 requisite ground for proposing the genus, and for referring these maxillary specimens to 

 the species Macropus Anak, originally founded on characters of the lower jaw and teeth. 



The upper molars of Protemnodon are more like those of Sthenurus Atlas than of 

 Macropus Titan ; they have a narrow prebasal ridge without the link. The oblique 

 ridge extending downward and backward from the inner and hinder angle of each chief 

 lobe is more definitely marked, and the two lobes are more alike than in Sthenurus 

 Atlas. The breadth of the crown in to 1 and to 2 of Protemnodon Anak (Plate LXXXIII. 

 figs. 5 & 8) is greater in proportion to the fore-and-aft length than in Sthenurus; and 

 the inner border of the two lobes (ib. figs. 6 & 9) is narrower and more sharply pointed 

 than the outer border (ib. figs. 4 & 7), in a more marked degree even than in Sthenurus. 



Proceeding to the characters afforded by the mandible and teeth (Plates LXXXV. & 

 LXXXVL), I have first to remark that the premolar (p 3 in all the figures), in its relative 

 antero-posterior extent to the molars which follow, rather exceeds that tooth in Sthenurus 

 Atlas. The proportion of p 3 in Protemnodon is much the same as in the Bettongs^ ; 

 it is not equal to that in Pendrolagus dorcocephalus^. As in this Tree-Kangaroo, the 



* Trp6 (before), r&fii <■> (to cut), ofiovs (tooth) — in reference to the sectorial form of the anterior molar or premolar, 

 t 4to, 1845, pp. 325, 327, Nos. 1513, 1519. J Ante, p. 170, fig. 18. § Ibid. fig. 16. 



