278 



from a socket, close to the symphysis, where sufficient of the cavity was exposed to 

 show that it expanded as it sank in the substance of the jaw. 



Putting aside for awhile the evidence of the nature of this specimen afforded by 

 others since received from Australia, I believe it may be of some interest and instructivc- 

 ness to show how far its determination can be carried, on the supposition that it is the 

 sole example of its genus or order. 



The mammalian character is seen at a glance by the complex crowns and rooted 

 implantation of the molars, and by the simple condition of the ramus of the jaw, as 

 of one piece of bone. The nonage of the individual to which the jaw has belonged 

 is recognized at the same moment. 



Of Mammalia corresponding in size with the parent of a young one having its newly 

 cut milk-series of teeth in a jaw 8 inches long, the number of genera is not great ; and 

 we may be excused for thinking that most of those which are now represented by living 

 species must be known. Of these we should be led at once to Cuvier's Pachyderms by 

 the shape and size of the teeth of our young giant. The broad complex crowns of the 

 molars show its herbivorous nature. The Tapir alone exhibits the bilophodont type of 

 the second and third milk-grinders, with the conical, partly trenchant, partly crushing 

 shape of the first ; but it developes, with these in the mandible, eight small front teeth, 

 of which the outermost pair are canines. A Rhinoceros of Sumatra or Java may show 

 a pair of large tusk-like lower incisors, but they are associated, in the milk-dentition, 

 with a smaller pair of mid incisors*. 



There is another and more significant difference which the present fossil evidence of 

 a large Herbivore presents in comparison with a specimen of the same age, or with the 

 same phase of dentition, of any existing species of like size. In the young Tapir, e. g., 

 with three deciduous molars in each mandibular ramus, and the germ of the next molar 

 lying in its formative cavity deeper and less advanced than in the present fossil, the 

 enamel has been worn from the summits of the first and second milk-molars so far as to 

 expose the dentine, and it is abraded obliquely backward from the summits of both ridges 

 of the third molar. 



So also in a young Rhinoceros in which the second and third milk-molars are in place, 

 the first and fourth being still " en germe" the enamel shows masticatory abrasion at the 

 summits of the two chief lobes of d 2 and d 3. Corresponding signs of the assumption 

 of vegetable nutriment in addition to that afforded by the mother's milk are visible in 

 young Equines and Ruminants with a stage of molar dentition corresponding to that 

 shown by the fossil under consideration. 



Now here, although the first, second, and third molars are well in place, and the 

 basal ridges of the fourth have risen to the brim of the socket, the enamel shows only 

 a linear trace of attrition on the ridges of the second molar (Plate XL. fig. 3, d 4, h, g), with 

 a very feeble trace on the anterior ridge of the third molar (ib. m 1) ; its hind ridge and 

 the crown of the first molar (ib. d 3) are untouched. The inference is that the young 

 * Owes's < Odontography,' p. 591. pi. 138. fig. 15, di, 1 & 2. 



