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off to an edge closely fitting the contour of the base of the crown of the tooth ; the 

 inner side of the horizontal ramus (fig. 2) at once descends with a gentle vertical con- 

 vexity, interrupted beneath the last and part of the penultimate sockets by the concavity 

 due to the inflected lower border (d, d'). The depth of the inner side of the ramus 

 behind the fifth (last) socket is 2 inches 9 lines ; in Nototherium Mitclielli it is 3 inches 

 6 lines. 



The portion of the base of the incisor-socket exposed by the anterior fracture (fig. 4, i) 

 gives a vertical extent of 1 inch, a transverse breadth of 4 lines. The bottom is smooth ; 

 the side-walls worm-eaten, with a tendency to longitudinal striation. External to this 

 part of the socket, about a line's distance, the dental canal is exposed, of a subcircular 

 section, 3 lines in diameter ; about the same thickness of the osseous tissue divides it 

 from the outer surface of the jaw. Two inches behind this part a small orifice pierces 

 the outer surface at the same distance below the middle of the outlet of the alveolus of 

 the molar (m ■, fig. 1). 



The colour of the fossil above described from the deposits near Lake Victoria is a rich 

 brownish yellow. The osseous tissue is massive, the bone heavy, but does not adhere to 

 the tongue. The minute cancelli are vacant, not filled up by mineral matter. The dental 

 canal contains the easily displaced lacustrine deposit. The Nototherian fossils from 

 Darling Downs are either of a deeper and duller brown colour, as in the first described 

 jaw (Plate XXXVIII.), or of a greyish mottled stone-colour, as in the third and fourth 

 specimens. 



C. Nototherium inerme, Ow. — The fossil (Plate XLII.) on which the species Nototherium 

 inerme is founded consists of a left ramus of the lower jaw, mutilated and abraded as in 

 most of the specimens from the river-beds and deposits of Queensland. The base of the 

 coronoid (fig. l,f), with the entry of the dental canal (fig. 3, o) and part of the inflected 

 angle (ib. b, e), remain at the hind end of the specimen, and the back part of the sym- 

 physis (figs. 2 & 3, s) terminates the fore end. The symphysis does not extend back- 

 ward beyond the vertical parallel of the fore half of the second molar (d The dental 

 canal (fig. 3, 0) begins near the level of the molar, and 1 inch 9 lines behind the last 

 alveolus. In the type mandible of Nototherium Mitclielli, as in the subjects of Plates 

 XXXVIII. & XXXIX., the orifice of the dental canal is raised above the level of the 

 grinders, and is 3 inches behind the last alveolus ; yet the antero-posterior diameter of that 

 alveolus is less in Nototherium Mitclielli than it is in N. inerme. The specific difference of 

 N. inerme from both N. Mitclielli and N Victories is also shown in the relative position 

 of the symphysis to the fully developed molar series. The absence of any trace of inci- 

 sive alveolus at the fractured part of the symphysis indicates the tooth to have been 

 relatively smaller, still less of the character of a tusk or weapon offensive or defensive ; 

 whence the specific name originally suggested by the present fossil*. The depth of the 

 horizontal ramus is relatively less than in Nototherium Mitclielli, and diminishes in a 

 * ' Catalogue of the Fossil Mammalia &c. in Mus. Coll. Surg.,' 1845, p. 314. 



