409 



Valley caves and freshwater beds of Australia. Figs. 1 & 14 in Plate LXXXIII. give a 

 side view, and figs. 2 & 4, Plate LXXXI. the grinding-surface, of the right series of 

 upper and lower molars of this animal, of the natural size. 



So much of the mandibular ramus of a Macropus Titan (Plate LXXXII. figs. 13-16) 

 as remains in the specimen in the Oxford Museum closely agrees, save in size, with that 

 of Macropus major (Plate LXXX. fig. 15). As in that recent specimen, the individual 

 affording the present fossilized relic had shed both the premolar and the two anterior 

 milk-teeth ; d 4 also shows a wear of crown and exposure of roots indicative of speedy 

 expulsion. The long diastemal border (between d i and i) is trenchant to near the 

 outlet of the incisive alveolus. It descends, more rapidly than in the living Kangaroo, 

 from the anterior molar socket, with a concave curve, reducing the vertical extent of the 

 symphysial part of the ramus at the outlet of the dental canal (ib. fig. 13, v) to two thirds 

 of that at the outlet of the anterior molar socket, d i. In advance of the dental canal 

 the symphysial part of the jaw is reduced to a mere case of the root of the long pro- 

 cumbent incisor, i. 



The descent is less sudden, and the concavity of the diastemal border somewhat less, 

 in another specimen of the mandible of Macropus Titan, which more closely resembles 

 in this respect the recent Kangaroo. 



The symphysial surface in Macropus Titan (Plate LXXXII. fig. 15) begins behind, in 

 advance of the vertical parallel of the fore part of the first molar socket ; it expands so 

 as to cover the lower half of the inner surface of the ramus at the part opposite the 

 outlet (v), and then contracts to terminate before attaining the outlet of the incisive 

 alveolus, at least as regards its grooving and other rough markings for ligamentous 

 union. The contrast between this structure of the symphysial joint and that in fig. G,« 

 [Sthenurus Atlas), is considerable, and supports the inference that the junction between 

 the right and left rami was not more close in the large Macropus Titan than in Macropus 

 major. The direction of the elongated socket of the incisor and the procumbent 

 position of that tooth in the fossil are as in the existing species of Macropus. The 

 crown of the incisor, so far as it is preserved, agrees in shape, relative size, disposition 

 of enamel, position and obliquity of the back part of the abraded working-surface, with 

 that of Macropus major. The configuration of both outer and inner surfaces of the 

 horizontal ramus, especially the ridge indicating the lower limit of insertion of the crota- 

 phyte muscle and extending a little L elow the margin of the ectocrotaphyte cavity, as 

 shown in Macropus major (Plate LXXX. fig. 15), are repeated in Macropus Titan (Plate 

 LXXXII. fig. 13, e). The last molar stands out more freely, or entirely, in advance of 

 the fore margin (ib. fig. 13, q) of the coronoid process in Macropus Titan than in 

 Macropus major (Plate LXXX. fig. 15) ; and it advances further as the animal grows 

 older and the molar series is further reduced. 



The inflection of the inner and lower border of the ascending ramus begins anteriorly 

 nearly in the same relative position. The anterior border of the intercommunicating 

 vacuities (Plate LXXXII. fig. 15, e, d) between the outer and inner cavities of the 



