279 



Herbivore represented by the fossil derived a greater proportion of its nourishment from 

 the mother, and much less from extraneous sources, than do the placental Herbivores 

 at a corresponding stage of immaturity. 



In this respect the fossil repeats the molar conditions of a young Kangaroo [Macropus) 

 at the same phase of dentition f. With this phase the existing marsupial herbivore has 

 attained that size and strength as a denizen of the pouch in which it begins to protrude 

 its head to crop, occasionally, a tender leaf or blade of grass while the mother may be 

 browsing or grazing. In the singleness and size of the sloping incisor, in the shape and 

 proportion of the first molar [d 3), as well as in those of the second and third two-ridged 

 grinders, d 4, & mi, the fossil more closely resembles Macropus than any other known 

 genus, whether marsupial or placental. 



I accordingly here pushed the comparative research a stage further, and removed the 

 outer wall of the jaw, as in fig. 5, Plate XL., to see if the large Australian bilophodont 

 fossil carried its correspondence with Macropus to the extent of showing the germ of a 

 premolar (p s)J ; but of this tooth there was no trace. The length and deep implantation 

 of the two fangs of d 3 (/), underlain by the expanded base of the procumbent incisor 

 (ib. i*), make it very improbable that such germ of &p 3 could ever be developed in the 

 species represented by the fossil. 



Thus the results of the above comparisons, independently of other evidences of Noto- 

 therium, would have led to the conclusion that the young Herbivore, notwithstanding 

 its bulk, belonged to a group of Mammals in which the milk-dentition was not so soon 

 brought into use for grazing or browsing as in the Placental series ; that it, therefore, 

 was probably a Marsupial ; which conclusion the close concordance in number and shape 

 of grinding-teeth with the largest existing Herbivore of that order (the Kangaroo) 

 would have put beyond doubt. 



The lower incisor, in the immature example, had pushed its tip, as has been said, 

 about two thirds of an inch from the socket ; it is of a conical form, with an obtuse 

 apex, which has been abraded for the extent of 3 lines (Plate XL. fig. 3, i'). The ename^ 

 coats the outer and under part of the tooth, bending up a little way upon the flat inner 

 side, and in an increasing degree as the tooth expands (Plate XL. fig. 4, e) : the enamel 

 is not continued to the open base (ib. fig. 5, i*) as in Diprotodon : the line of termina- 

 tion is well defined. A thin layer of cement coats the rest of the tooth's circumference. 

 The fracture of the exposed crown of the tooth gives a subquadrate surface, longest 

 vertically, with the lower and outer angle rounded off. The two diameters are here 

 6 lines and 5 lines ; but the vertical diameter of the hollow base exceeds an inch, the 

 length of the entire though incomplete tooth being 2 inches 9 lines. It is directed 

 obliquely forward and upward, at an angle of 140°, with the lower border of the ramus ; 

 a rather less open one than in Diprotodon. 



t Owen, Art. " Teeth," Cyclopaedia of Anatomy &c, fig. 594, B ; and < Anatomy of Vertebrates,' vol. iii. 

 fig. 296, B. 



+ Page 209, fig. 4, p s. 



