474 
SIR R. OWEN ON THE FOSSIL REMAINS OF TWO SPECIES 
borders of the partially divided passages. This seemingly second floor also extends 
beneath the floor of that fore part of the outer nostril, as it were, undermining it, and 
contracting to a blind end two-thirds of an inch in advance of the overlying base of 
the partial bony “ septum narium ” (fig. 6, ol). The smooth surface of the naso-palatal 
cavity extends outward and downward on each side of the above part of the floor and 
behind the outer ends of the hinder trenchant walls of the alveolar channels. 
The thickness of the jaw-bone forming the side walls of the palatal tracts at a 
transverse line drawn across the lower floor (fig. 6, g) of the nasal chamber is two- 
thirds of an inch. The fracture of this part of the upper jaw on the right side exposes 
a small smooth-surfaced sinus (fig. 5, i). The under-surface of the mid-portion 
(fig. 4, g) of the bony palate shows a pair of depressions (ib., I, l), from each of 
which a small canal is continued into the substance of the upper jaw. 
If the fossil above described (Plate 29, figs. 3-6) be compared with the corresponding 
part of the skull of Megalama prisca ,* the bony narial septum will be seen to be 
similarly incomplete, dividing the lower half only of the nostril. The trenchant 
border of the beak (fig. 3, Plate 38, ib.) is similarly incomplete ; the trenchant 
border of the upper mandible of Megalania shows also a median notch, which I 
deemed might be “ due to accident” (tom. cit., p. 1043), but it is only partially so. 
If the under-surface of the fore end of the upper jaw of Meiolania (fig. 4) be com¬ 
pared with that part of Megalania (fig. 3, Plate 38), the difference, added to those 
already and subsequently noticed in other parts of the skull, may be admitted to 
exceed mere specific distinction. The second trenchant ridge in Megalania is co¬ 
extensive and parallel with the outer one, and is followed by a third nearly parallel 
ridge, but lower, and of less extent. In both Reptiles these ridges were, most 
probably, sheathed with horn, as in the Chelonian Reptiles. The bony roof of the 
mouth is continued in Megalania a short way behind the third trenchant ridge. The 
narrower medial backward production of the bony palate has not, in Megalania, the 
mid-longitudinal rising with the lateral and perforated depressions as in Meiolania. 
The anterior transverse curve of the upper mandible (premaxillaries) is greater in the 
smaller edentulous Saurian. 
The partial bony septum (fig. 3, ol) terminates obtusely in Meiolania without trace 
of fracture. The vertical extent of the fore and outer plate of the upper jaw in 
Meiolania is relatively greater than in Megalania, and no trace of the outer channel 
impressing the interspace between the nostril and orbit is present in the portion of 
Meiolanian skull above described.! 
Plate 30 represents the upper surface, natural size, of the portion of the skull of 
Meiolania platgceps which could be exposed in the block of matrix in which it was 
buried. The skull had suffered fracture, with some dislocation of parts, but retained 
* ‘ Phil. Trans.,’ 1880, vol. 171, Plate 37, fig. 1, and Plate 38, fig. 3. 
t See Plate 38 tom. cit., fig. 1, o n. 
