401 



transmitted to me by my friend Geokge Benjstett, M.D., F.L.S. This is interesting as 

 evidence of the range of the large and now extinct species : the bone shows the usual 

 state of petrifaction of fossils from that formation and locality. It is a portion of the 

 left maxillary bone, with a series of five molars in situ. The first (Plate LXXXI. figs. 

 6, 7, 8, d 2), slightly mutilated externally, has a simple subcompressed unilobate (or sub- 

 bilobate ?) crown, broadest behind, of much smaller size than that of the following 

 two-ridged grinder (d 3) ; its "working-surface had been worn so as to expose a broad 

 field of dentine. The next tooth (^3) shows a minor degree of abrasion, the third 

 molar (d 4) still less. In the fourth (m 1) the summits of the two transverse ridges have 

 just been touched ; those of the hindmost molar (m 2) in place had not come into use, 

 although they attained nearly the level of the ridges of the antecedent tooth. More- 

 over, behind the fifth molar was the fore part of a smooth subspherical cavity (ib. fig. 9), 

 plainly the formative alveolus of another molar [m 3) still to come into place. 



Accordingly the five molar teeth in this maxillary fossil I interpreted as homotypai 

 in the upper jaw with the five molars in the lower jaw of a similarly immature Macro 

 pus major. Adopting the symbols in fig. 296, d, vol. iii. of my ' Anatomy of Verte 

 brates,' those of the five teeth in the present fossil would be : — d 2, d 3, d 4, m 1, & m .'. 

 To test this conclusion I proceeded to remove the outer table of the jaw-bone above d . 

 and detected the germ of p 3 (ib. fig. 6), in a stage of development like that of p 3 in 

 the lower jaw of the type specimen (Plate LXXXII. fig. 18), and corresponding with the 

 state of the dentition in the upper jaw of Macropus erubescens (Plate LXXX. fig. 6). The 

 back tooth, when formed in the hindmost closed alveolus, would be m 3, completing the 

 total of seven teeth developed in the molar series of the Macropodidce. 



In the upper premolar of Macropus Titan the crown consists of two simple, conical, 

 subcompressed lobes, the hindmost being thickest posteriorly ; it is supported on *vo 

 roots, the formation of which had commenced in the specimen described : its movement 

 into place, or into the masticatory series, would have involved the shedding of d 2 and 

 d 3 ; its crown would then contrast with that of d 4 by its freshness or freedom from wear. 

 The convexity of the outer surface of the two lobes, and the depth of the dividing in- 

 dent, accord with the characters of the lower premolar of the type specimen of Macropus 

 Titan expressed in fig. 18, Plate LXXXII. 



The bilophodont* upper molars of Macropus Titan (Plate LXXXI. fig. 8) show a well- 

 developed " prebasal ridge " connected by a " link " of enamel with the fore part of the 

 front lobe, near the middle and inclining rather toward the inner angle. In Sthenurus 

 Atlas (Plate LXXXIV. fig. 6) this link is feebly if at all developed. 



The mid link connecting the two main lobes in Macropus Titan (Plate LXXXII. fig. 11) 

 is rather sinuous and tumid ; it is better developed in this species than in Sthenurus 

 Atlas (Plate LXXXIV. fig. 6). The oblique posterior ridge (Plate LXXXII. fig. 11, 

 m 3, g, and Plate LXXXI. fig. 18, t) is strongly marked, and defines a depression at that 



* This term signifies not only that the crown is composed of two principal ridges or lobes, but that these 

 are transverse in position. 



