420 



associated with the same general pattern of working-surface of the molars dt,mi-t, 

 except that the fore-link and mid-link, though feebly developed, are more neatly defined 

 and readily recognizable in the small existing Kangaroo. The figures of both these 

 recent and fossil Kangaroos, or " Wallabies," being of the natural size, preclude the need 

 of stating dimensions. 



A portion of the right and a portion of the left maxilla of two individuals of 

 Sthenurus Atlas (Plate LXXXVIII. figs. 1-4), each containing the premolar and con- 

 tiguous 2-ridged molar, confirm the characters of the singularly modified premolar of 

 the smaller species on which the genus was founded. The outer surface between the 

 fore and hind convexities is traversed by three vertical ridges and four grooves in both 

 specimens, the hindmost ridge being the smallest and shortest. The oblique cavity 

 between the outer and inner wall is also crossed by three low short ridges, the inter, 

 spaces of which form small pits. 



In one specimen the size of the two teeth correspond with that of the maxillary 

 type (Plate LXXXIV. figs. 4-6) ; in the other the teeth are rather smaller, probably 

 having come from a female specimen. 



Sthenurus Atlas was first indicated by a fragment of the under jaw from the Breccia- 

 cave in Wellington Valley. In this (mandibular) type specimen (Plate LXXXII. 

 figs. 3 & 4) three molars (d 3, d 4, and m i) are in place ; the penultimate molar (m 2) is 

 lost ; the crown of the last molar (m s) is just rising from the formative alveolus. 



The first true molar (m 1) affords an instructive comparison and contrast with that in 

 the type specimen of Macropus Titan (ib. figs. 17, 18, mi). The grinding-surface of 

 m 1 in Sthenurus Atlas is broader in proportion to its length, especially behind. The 

 prebasal ridge is narrower and lower ; a simple link descending from the fore and outer 

 angle of the front lobe slopes straight to the middle of the summit of the prebasal 

 ridge. 



The outer convex borders of the two lobes (ib. fig. 4, m 1) are narrower than in 

 Macropus Titan (ib. fig. 18, m 1), and maintain their breadth, like columns, more uni. 

 formly to their summits. The inner borders are rather broader below, but are narrower 

 than in Macropus Titan. In Sthenurus Atlas the valley between the lobes is both wider 

 transversely and deeper, the link being lower ; it slopes from a point rather external to 

 the middle of the front surface of the hind lobe, and runs almost straight down to the 

 middle of the base of the hind surface of the front lobe. The mid link becomes almost 

 obsolete in the last molar (ib. fig. 3, niz). The summits of the lobes bend slightly back- 

 ward vertically, and from the thickening of the outer and inner angles are feebly concave 

 across anteriorly. There is a slight swelling of the base of the hind surface of the hind 

 lobe, but not any distinct postbasal ridge. 



I have given a new figure of the side view of part of this fossil (Plate LXXXII. fig. 4)*, 

 and an upper view of the entire fragment (ib. fig 3), showing the characters of the 

 working-surface of the molars. 



• It is shown entire from this view in " Mitchell," op. cit. 1st ed. voL ii. pi. xxix. fig. 1. 



