246 
PROFESSOR OWEN ON TEETH OF A LARGE EXTINCT GENUS. 
formation the most instructive specimens of Megalania have been obtained. With 
this verification of the subjects of the casts, I no longer defer making known so 
singular an addition to the, most probably, Marsupial fossil Fauna of Australia. 
The specimen from Kings Creek, though mutilated at both ends, includes a 
portion of the tooth, 2 inches 9 lines (70 millims.) in length, with an uniform breadth 
of 1 inch 3 lines (32 millims.), and as uniform a thickness of 7 millims. gradually 
increasing to 8 millims. at both side-margins. The curvature of the tooth is uniform 
and moderate, and is shown in Plate 11, fig. 1. 
Sufficient of the pulp-cavity was preserved at one end to indicate the tooth to have 
been one of uninterrupted growth ; at the opposite end the cavity is reduced to a 
linear fissure, fig. 3 a. Here the body of the tooth is seen to be composed of hard 
dentine, with a coat of enamel on the convex side, bending for the extent of a millimetre 
upon each obtuse margin ; the rest of the tooth having a thinner coat of cement. 
One margin, slightly broader and less rounded than the other, indicates that which 
was in contact with, or very close to, the fellow incisor of the scalpriform pair. 
The enamelled surface of the tooth presents fine and close-set longitudinal striae; 
its transverse convexity is less than the corresponding concavity of the opposite side. 
The concavity is traversed lengthwise by a pair of low, linear, risings or ridges, 
r, r, fig. 2, 5 millims. apart; one extending midway between the two borders, the 
other ridge being nearer the outer lateral border. Most of the surface of this fossil 
shows a deep rufous stain which extends some way into the tooth’s substance, as 
shown by the sections for microscopical research next to be noted; the weight of 
the fossil indicates metallic infiltration. 
Of the intimate structure of the teeth of Marsupicdia I detected, in 1844,'"' but 
two which seemed to call for illustration : one, from the Wombat, showed a larger pro¬ 
portion of the cement exterior to the enamel than in the Rodents’ incisors : this 
character, as it was exaggerated in the molars, was exemplified in a longitudinal section 
of one of those teeth (op. cit., plate 103, fig. 2). The other Marsupial modification 
was displayed by the teeth of the Kangaroo, and the illustration was afforded by a 
section of an incisor. The character in question is a continuation of the more wavy 
terminal portion of the dentinal tubes across the boundary-line into the enamel 
(op. cit., plate 102). In the subjoined drawing of a similar microscopic section of the 
fossil incisor of Sceparnodon the resemblance to the Wombat (ib., plate 103), in the 
dental character so exposed will be seen to be closer than to any other Marsupial or to 
any Australian genus of Rodent. The existing members of the Rodentia, native to 
Australia, are mostly of small size : the aquatic form, Hydroinys, exemplifies the 
largest, but this hardly exceeds that of our Water-Rat (Arvicola) , in which the upper 
incisors show a greater fore-and-aft than transverse diameter. The small relative 
degree of the former diameter, or thickness, of the tooth is peculiar to Sceparnodon. 
* ‘ Odontography,’ pp. 373-398; plates 98-103. 
