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in the horizontal portion, the other in the ascending portion, or " ramus." It may well 

 be that this character, which is not present in Kangaroos and Wombats, may be pre- 

 sented by Biprotodon, when a perfect mandible of that animal is obtained ; but if the 

 fore part of the inflected border shown in the subject of Plate XXVII. fig. 2 be the 

 beginning of an anterior inflection divided by a non-inflected tract from the posterior 

 inflection, which represents the inflected angle in Macropus and Phascolomys, such 

 beginning is more posterior in position, more nearly where the angular inflection begins 

 in Nototherium. In the adult jaw of N. Victorice (Plate XLI.)and in the immature one 

 of N. Mitchelli (Plate XL.) the whole extent of the anterior inflection (d) is shown ; 

 only, in the adult specimen, the free border has suffered. 



The orifice of the dental canal is raised to a level above that of the summits of the 

 last molars in Biprotodon. The largest of the species of Nototherium differs little in 

 this respect ; but in N. Victorice and N. inerme the orifice is brought down to, or near 

 to, the level of the alveolar outlets. In the smaller existing herbivorous Marsupials it 

 is placed still lower, being hidden in an excavation which does not exist in the extinct 

 pouched herbivorous giants. 



Of the position of the condyle we can speak only as it is indicated in Nototherium 

 Victorice. Here it is raised high above the level of the molar series, as in all herbivorous 

 Marsupials, but not so much raised relatively as in Biprotodon. 



In the curve by which the coronoid process advances and rises from the fore part of 

 the neck of the condyle, Nototherium resembles Phascolomys more than it does Macropus, 

 in which the process rises in almost a straight line obliquely forward to its pointed apex. 



§ 4. Bentition. — The dental formula of Nototherium, as of Biprotodon, is i \=^, c ~, 

 m ~= 28. The homologies of the molars with those of diphyodont Mammals are 

 given by the symbols d s, d *, m i, m 2, m 3, by which those teeth in the present paper 

 will be signified as they range from before backwafd *. 



The upper incisors, i ., i 2, i 3 (Plate XXXVI. fig. 1, Plate XXXVII. fig. 3), follow 

 one another in the same direction in each premaxillary, the foremost being the largest 

 and the sole pair visible in a front view (Plate XXXVI. fig. 2). The right and left 

 series run nearly parallel, slightly converging posteriorly ; the greater interval between 

 the right and left incisors of the second and third pairs is due to their smaller size, and 

 their outer surface ranging with that of the larger exterior pair (Plate XXXV I. fig. 3, 22*). 

 In the old Nototherium Mitchelli the first incisor does not project beyond an inch from 

 the socket, the crown being directed downward very slightly forward and outward. The 

 entire tooth (Plate XLIII. figs. 1 & 2) is 5 inches 1 line long in a straight line, 1 inch 

 7^ lines in the greatest (fore-and-aft) diameter, which is about the middle of the root, 



* In my Memoir on Nototherium (Quarterly Journal of the Geological Society, vol. xv. 1859), I state, in 

 regard to these molars, that " the first appears to be a premolar and the rest true molars" (p. 171). I am now 

 able to adduce [Plate XL. fig. 5] evidence that the first tooth is the homologue of d 3 in Macropus, and has no 

 vertical successor —p s. 



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