424 



to m l, at a distance varying from 2 lines to 5 lines below the alveolar border. Below 

 the channel the ramus swells to greater thickness than in the largest of the mandibular 

 fossils of Macropus Titan. The lower border has been broken away; and in the longi- 

 tudinal extent of mandible here preserved, the fractured surface shows a pretty uniform 

 breadth or thickness of 9 lines. 



The increase of the fossil (Plate LXXXIV. fig. 7) over the younger Sthenurus (Plate 

 1AX\ 1 1 . fig. 5) is shown by the bone more than by the teeth. But even in the smaller 

 specimen (ib. tigs. 5, 6) the mandible is relatively stronger and deeper than in Macroglia 

 Titan (ib. figs. 13, 15). In this species the last four molars (d 4 and m s) occupy a longi- 

 tudinal extent of 2 inches 4 lines, but in Sthenurus Atlas of 2 inches. These differential 

 mandibular and dental characters come well out in comparing figs. 5 & 13, and figs. 

 8 & 14, in Plate LXXX1I. 



§ 8. Sthenurus Brehus, Ow. — This species is represented by two fossils from the 

 Breccia-cave of Wellington Valley, presented to the British Museum by the Trustees of 

 the Natural-History Museum of Sydney, New South Wales, and forming part of the 

 results of the exploration by Prof. Thomson and Gerard Krefft, Esq., carried out 

 with the aid of the legislative grant*. 



The specimens formed part of a series of duplicates, thickly encrusted, like those of 

 Thylacoleo and Phascolomysf, with the reddish stalagmite of the cave. 



The most acceptable and instructive results of the clearance of the fossils from their 

 matrix were the subjects of figs. 5-9 of Plate LXXXVII. The largest specimen (figs. 

 5 & G) consists of a portion of cranium including a great part of both maxillaries, with 

 the intervening palatal plates and both palatine bones ; the zygomatic masseteric process 

 came out entire on both sides of the skull. The molar series of the left maxillary 

 (p 3 to m 3) had undergone fracture of the crowns of the two anterior teeth ; the portion 

 of the right maxillary included the two posterior molars. 



The pattern of the molar crowns closely accords with that of Sthenurus Atlas, and 

 the narrow but well-defined prebasal ridge (ib. fig. G, m hf) was without the link ; the 

 mid-link (ib. ib. r) was represented by a rudiment at the bottom of the valley between 

 the two transverse lobes, a, b ; the postbasal ridge (y) was represented by the crescentic 

 border of a depression on the hind surface of the hind lobe ; the main ridges were 

 rather narrow antero-posteriorly in proportion to their breadth and vertical extent. 



The superiority of size of Sthenurus Brehus over Sthenurus Atlas may be estimated by 

 comparing figs. 5-9, Plate LXXXVII., with figs. 4-6, Plate LXXXIV. The base of 

 the broken premolar (Plate LXXXVII. fig. 6,^> 3) shows similar proportions of that tooth, 

 although, as the crown swells out beyond the part retained, this does not yield the whole 

 for e-and-aft extent. Fortunately another cranial fragment of the species (Plate LXXXVII. 

 figs. 7,8, 9) included the premolar and adjoining molar entire, and yielded the required 

 subgeneric character of the auterior tooth. The crown is 10 lines in fore-and-aft length, 

 5£ lines in vertical extent, 4^ lines across the thickest part of the base, which is near 

 * Ante, p. 239. f Ib. P- 319. 



