OWEN NOTOTHEKIUM. . 171 



show this relation, as weU as the Kangaroo, "Wombat, and Koala 

 (fig. 2, z) ; and the temporal fossa is of considerable capacity, as it also 

 is in the great Diaothere, which has the same type of molar teeth. 

 The worldng of opposed double -ridged molars evidently requires 

 a greater amount of muscular action than that of the more complex 

 but flatter molars of the Ruminants, Horse, Rhinoceros, and Elephant. 



The maximum development of the zygomatic arches, in connection 

 with grinding teeth of the type of those of the Kangaroo and Tapir, 

 is manifested by a most extraordinary Marsupial Herbivore, of the 

 size of an ox, the cranium of which has recently been discovered in 

 Pleistocene deposits at King's Creek, Darling Downs, Australia, and 

 is now in the Museum at Sydney, N. S. Wales. 



I am indebted to my friend Mr. George Bennett, F.L.S., for four 

 carefully-made, and apparently most accurate, outline -drawings of 

 this unique fossil, in which so much of the anatomical characters are 

 given as have enabled me to make the requisite comparisons for 

 a conclusion as to the nature and affinities of the, most probably, 

 extract Australian quadruped. The dentition of the upper jaw 

 consists of three incisors and five molars on each side, of which the 

 first appears to be a premolar and the rest true molars : i. e., i. ^—^, 

 c. ^zi2, jp. Lzi, m. Izi^ ; agreeing, in this formula, with Macrojous and 

 JDiprotodon. 



The reduced size of the drawings does not permit one to infer 

 more than a close general resemblance of the transversely-ridged 

 molars of the fossil with those of JDiprotodon and Macropus. 



The modifications of this dentition resemble those of the Dijproto- 

 don* in the retention of the premolar after the last true molar has 

 come into place, and in the superior size of the first as compared 

 with the second and third incisors. From so much of the sockets of 

 the first incisiors as is indicated in a front view of the cranium, it 

 may be inferred that they were scalpriform teeth, implanted by a 

 long, simple, slightly- curved base, of equal diameter with the crown. 

 Each lateral series of grinders is slightly curved with the convexity 

 outward ; the two series converge a little forward. 



All the grinding teeth are worn ; the anterior most, and the 

 rest by degrees less, to the hindmost, which is least abraded : this 

 indicates the course of their succession, and throws clear light on 

 the ordinal afGbiities of the fossH. 



In the Tapir, as in other placental terrestrial Herhivora, the 

 number of true molars being |^, and the first of these, m i (Plate 

 YIII.fig.4) coming into place and use before the last premolar jp 4 (ih), 

 the first molar presents a more worn grinduig- surface than the tooth 

 which precedes it, p 4 : in the Kangaroo and other Marsupial Her- 

 hivora, the number of true molars is ^=^ ; and, as they succeed each 



other from before backwards, the first of the four is always more 

 worn down than the second, thus presenting conditions of the grind- 

 ing- siuf ace the reverse of those which would be presented by the 



* See " Report on the Extinct Mammals of Australia," in ' Report of the 

 British Association,' 1844. 



