232 REPORT — 1844. 



any canal leading to the outer surface of the ascending ramus, as in the 

 Wombat and Kangaroo ; but this external opening is not present in all Mar- 

 supials. The anterior outlet of the dental canal is smaller than in the Mas- 

 todon, and being placed more forwards, resembles that in the Elephant. The 

 number, and apparentlj' the form of the teeth, approximate the Australian 

 Pachyderm more closely to the Mastodon than to the Elephant, but the equal 

 size of the last and penultimate teeth, which had the same number of divi- 

 sions of the crown, are points in which the extinct species represented by the 

 present jaw still more nearly resembled the Diprotodon, the Tapir and the 

 Kangaroo. 



In its general shape the fossil jaw in question differs widely from all existing 

 Marsupials and all known ordinary Pachyderms, and in the chief of these 

 differences it resembles the lower jaw of the Proboscidians. It resembles 

 these however, in common with the Wombat, in the forward slope and cur- 

 vature of the posterior margin of the ascending ramus extending from the 

 condyle to the angle of the jaw, in the inward production of the post-molar 

 process, in the position of the base of the coronoid process exterior to the 

 hinder molar, in the thickness of the horizontal ramus, as compared with its 

 length, and the convexity of its outer surface ; and it also resembles the Pro- 

 boscidians, in common with the Kangaroo, in the small number of the grinding 

 teeth. From the lower jaw of the Kangaroo and Wombat the present fossil 

 differs in the absence of the deep excavation on the outer side of the ascending 

 ramus, which, in those Marsupials, leads to a perforation in the base of that 

 part of the jaw ; and it also differs in the inferior depth of the inner conca- 

 vity, and the inferior extent of the inward production of the angle of the jaw, 

 besides the more important difference in the absence of the large incisor tooth. 

 From the jaw of the Diprotodon, the present fossil differs in the much smaller 

 vertical extent of the symphysis, and in the convexity of the jaw at its outer 

 and anterior part, and more essentially in the absence of the incisive tusk and 

 its socket ; but it must have closely resembled the Diprotodon in the general 

 form and proportions of the molar teeth. On these grounds I propose to in- 

 dicate the genus of the fossil Mammal to which the above-described lower 

 jaw belonged by the name of Nototheriurn, and the species as inertne, from 

 the absence of the incisive tusks. 



Species 2, N. 3Iitchclli. 



The posterior half of the ramus of the lower jaw of a second species of 

 Nototheriurn, wanting the condyloid and the upper part of the coronoid pro- 

 cesses, and containing the last two molar teeth ; the crowns of these teeth are 

 much fractured, but demonstrate that they were divided into two principal 

 transverse ridges. The antero-posterior extent of both teeth together is three 

 inches three lines, the last molar being two lines longer in this dimension than 

 the penultimate one : its transverse breadth is one inch two lines. The den- 

 tine of the crown is encased in a sheath of enamel of nearly one line in thick- 

 ness, with a smooth and polished surface, impressed at the outer part and near 

 the base of the tooth, where the enamel is principally preserved, with fine 

 parallel and nearly horizontal transverse lines. 



Part of the abraded surface of both transverse ridges is preserved in the 

 penultimate grinder, showing that they had been more thau half worn away 

 by mastication at the period when the animal perished. The smooth and 

 polished exterior of the enamel covering the anterior part of the posterior 

 eminence presents a striking contrast to the reticulo-puuctate character of the 

 enamel, at the corresponding part of the molar in the Diprotodon, which in 

 the general form and proportion of this part of the jaw so closely agrees with 



