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Suborder DIPROTODONTIA. 



Family GRAVIGRADA. 

 Genus Notothekium. 



§ 1. Introduction. — The recognition of the genus which is the subject of the present 

 Section was subsequent to that of Diprotodon. So much of the molar teeth as remained 

 in the mutilated mandibles* transmitted to me, in 1842, by Sir Thomas Mitchell, C.B., 

 from the bed of the Condamine River, indicated their transversely two-ridged character, 

 and suggested at first sight that the fossils might belong to some smaller species of 

 Diprotodon. Closer scrutiny, however, showed them to be parts of full-grown animals, 

 and that they could not be the young of any larger extinct Herbivore. 



Moreover, sufficient of the symphysial or anterior part of one of the mandibular 

 fossils remained to demonstrate the absence of any incisor developed as a tusk or defen- 

 sive weapon f, such as coexisted with the bilophodont molar teeth in the lower jaw of 

 Diprotodon. The small portions of the enamel on the remaining bases of the molars 

 (for the crowns of all had been more or less broken away) showed a smoother surface 

 than that at the corresponding parts of the molars in Diprotodon. I was therefore led 

 to recognize with much interest, in the fossils transmitted by my esteemed friend on 

 his return to his duties as Surveyor General of the Colony of Australia, after the 

 publication of the work J containing the first notice of Diprotodon, evidence of another 

 genus of extinct herbivorous marsupials, second only in bulk to that first discovered, and 

 I proposed for the smaller genus the name of Nototherium^. 



Further comparison of the mandibular fossils referable to such genus indicated them 

 to have belonged to two species, to one of which (Woodcut, fig. 1, p. 250)1 was glad to 

 attach the name of its discoverer (Nototherium Mitchclli) ; the other I proposed to 

 call Nototherium inerme, as it afforded evidence of the absence of large incisor tusks. 

 Whether any, or of what proportion, or in what number, incisors might have been 

 present in the missing fore part of the fractured symphysis could not, of course, be 

 determined ; that which remained only gave the negative evidence as to incisors of the 

 relative size and shape and persistent growth characterizing the Diprotodon || . 



* Owen, " Report on the Extinct Mammals of Australia, &c.," in Reports of the British Association for the 

 Advancement of Science for 1844, 8vo, p. 223, plates 3 & 4. 

 t lb. p. 231. 



+ ' Three Expeditions into the Interior of Eastern Australia,' vols. i. & ii. 8vo, 1838. 



§ i-oros, south, dnplov, beast, ' Catalogue of the Fossil Mammalia and Aves in the Museum of the Royal Col- 

 lege of Surgeons,' London, 4to, 1845, p. 314. 



|| " The lower fractured surface exposes the dental canal extending obliquely from without inwards below the 

 sockets of the anterior molars and then bifurcating ; the outer and larger division terminating at the mental 

 foramen, and an inner and smaller one extending forwards nearer the symphysis, but without any trace of a 

 large incisor " (op. cit. p. 319). 



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