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In a visit this year to the Geological Museum, Oxford, I was much gratified and 

 interested in finding, in the series of fossils from the freshwater deposits of Darling 

 Downs presented by Sir Chaeles Nicholson, Bart., M.D., evidence of which I had been 

 long in quest, of the fully, or nearly fully, developed dentition of the lower jaw of 

 Sihenurus Atlas. Through Professor Phillips's kind permission, this unique fossil forms 

 the subject of figs. 5-8, Plate LXXXII. It is a left mandibular ramus, wanting the 

 ascending branch, of a nearly mature individual of Sthenurus Atlas. 



The last molar (m 3) has risen into place, and the summits of its transverse lobes have 

 been just touched by masticatory abrasion, acting from above obliquely backward, 

 without exposing the dentine ; but the large and characteristic premolar (p 3) has not 

 risen beyond the level of the basal third of the crown of the adjoining molar (d 4), and 

 its summit is quite unworn. 



This specimen, moreover, gives the mandibular characters of the genus Sthenurus as 

 distinguished from those of Macropus (ib. figs. 13, 15) — as, e.g., the shorter sym- 

 physis (fig. 6, s), the larger extent thereon of the articular surface (which reaches to the 

 outlet of the incisor socket), the angle which its lower border makes with that of the 

 horizontal ramus, and the continuation of the upper or diastemal border to the 

 incisor outlet in a direction more nearly parallel with that of the molar alveolar border, 

 not descending so much or so abruptly from that border as it advances forward. 

 The outlet (ib. fig. 5, v) of the dental canal is nearer the molar series, and the part of 

 the jaw anterior to the outlet is shorter than in Macropus Titan. The depth of the 

 ramus behind the last molar (m 3) is relatively greater. The inner surface of the hori 

 zontal ramus (ib. fig. 6) is less convex vertically than in Macropus Titan. 



The symphysial surface, though free or unanchylosed in the not quite mature indi- 

 vidual yielding the specimen, must, from its greater vertical extent and uniform flat- 

 ness, fit closer to its fellow, and permit less divaricating movements of the two rami 

 than in Macropus. Besides the anterior outlet (ib. fig. 5, v) there is a vascular foramen 

 below m 1, midway between the alveolar and inferior borders of the ramus ; but this 

 may be an individual character. 



The broken border of the ascending ramus shows the fore half of the margin of the 

 wide intercommunicating foramen (ib. fig. 6, e), and the fore part of the large cavity 

 from the inner half of which the dental canal is continued forward. 



The postalveolar platform has a sharper inner border, and forms a more marked 

 angle at that border, than in Macropus, indicating the place of the postalveolar process 

 in Nototherium, to which, in the form and proportions of the symphysis, its closer and 

 firmer junction of the rami, as well as in the characters of 3, the present genus offers 

 a nearer approach than does Macropus proper. Moreover, as the socket of the incisor 

 follows the direction of the symphysis, the tooth projects less horizontally than in 

 Macropus, and rises at a similar angle with the horizontal lower border of the 

 ramus. In all the characters of the symphysial end of the mandible Halmaturus 



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