269 



Mr. Keefft has favoured me with a pencil-sketch of the base of the incisor (Cut, 

 fig. 2, i), of the natural size, from the original fossil, showing the exhaustion of the pulp 

 in this tooth of limited growth. 



B. Nototherium Victoria?, Ow. — In the specimen of the Fig. 2. 



left ramus of the mandible (Plate XLL), liberally trans- 

 mitted for my examination by direction of the Trustees 

 of the Museum of Natural History in Adelaide, South 

 Australia, more of the ascending ramus is preserved than 

 in any of the foregoing specimens ; and there are differ- 

 ences which deserve to be interpreted as specific. 



The specimen was discovered by Mr. Tilgate, of Went- 

 worth, South Australia, in freshwater deposits near Lake 

 Victoria, in that colony. 



The posterior orifice or entry of the dental canal (fig. 2, o) 

 is on a level with the outlet of the last alveolus (m 3), not 

 perforating the base of the coronoid above that level as in 

 Nototherium Mitchelli. The inflection of the lower border 

 (ib. d, d', d') begins on a vertical parallel with the hind lobe 

 of the penultimate molar (m 2), and terminates a little 

 behind the vertical parallel of the last alveolus, before 

 the horizontal ramus bends upward into the base of the Fractured symphysis of jaw, -with 

 ascending ramus. After a subsidence for the extent of base of broken incisor, Nototherium 

 an inch and a half, the lower border again begins to be MitcMh. 

 inflected, suddenly (at a e), and to a greater degree than at any part of the more posterior 

 inflection in Nototherium Mitchelli (Plate XXXIX. fig. 1, a). The second inflection 

 in the present species, at first as thick as the anterior one (viz. 5 lines), quickly thins off 

 as it recedes to a plate of 1 line in thickness (Plate XLI. e) ; which, after the course of 

 about an inch, suddenly expands to form the thick inner part (n) of the broad posteriorly 

 flattened hind surface of the ascending ramus, supporting the condyle (c). Much of this 

 joint is broken away, but both the outer and inner beginnings of its base or " neck " 

 remain, together with the entire extent of the base of the coronoid plate (fig. 1, q, r)> 

 the summit of which is also wanting. The concave platform (fig. 2, u) between the 

 fore part of the coronoid process and the postalveolar ridge and process has a breadth 

 of about an inch and a half; the process, as usual, has suffered fracture. 



From the back part of the last alveolus to that of the base of the process is 1 inch 

 5 lines ; from the same part to the dental orifice (0) is 2 inches 2 lines : the dental 

 canal runs obliquely forward ; only the two anterior thirds of the orifice are defined by 

 a sharp border ; the diameter of the orifice is 4 lines. A groove (fig. 2, p) of the same 

 breadth, and about an inch and a half in length, runs forward along the under and inner 

 side of the orifice (0) ; this groove has a sharp inner border. A parallel ridge is directed 



