PROFESSOR OWEN ON THE AFFINITIES OF THYLACOLEO. 
577 
the foremost tooth, i 1 , and the carnassial, p 4, in Thylacoleo. But to which of them 
the term canine may be assigned is doubtful. Relative size might weigh with the 
largest of these intermediate teeth, i 3, but its trenchant character is repeated in the third 
incisor of the existing Kangaroos : it is not a cuspidate tooth as restored in outline at 
c, in Plate 14 of the Paper of 1871. I have nothing to alter or add to former 
descriptions of p 4 and to 1 (ib., ib.). In existing Diprotodonts the latter tooth has a 
broad tuberculate or ridged masticatory crown, and is followed by three similar molars, 
absent in Thylacoleo. 
Of the extreme modification of the Diprotodont type for carnivorous work I hold the 
opinion expressed in the former Paper (1871), and have only to add that the retention 
of the seemingly functionless teeth, i 2 —p 3, crowded together in the upper jaw, is 
significant of a principle underlying the adaptive explanation. 
Dentition of the lower jaw of Thylacoleo.—In the portions of mandible of Thyl. 
carnifex, figured in Plates 12 and 13 of the Paper of 1871, the dental formula was 
inferred, as in that of the upper jaw, from sockets of teeth. I am now able to submit 
three views of the entire dentition of a fossil mandible (Plate 39, fig. 2 ; Plate 41, figs. 
1 and 2) discovered in contiguity with the subject of fig. 1, Plate 39. 
The foremost laniariform tooth, i 1 , repeats the shape and size described (pp. 226? 
227) and figured (Plate 13, figs. 4-7, Paper of 1871) from a cast transmitted to me in 
1870, of a tooth in the Museum of Natural History, Sydney, which was obtained by 
Mr. Krefft from “a breccia cavern, Wellington Valley”; and its characters might 
well condone the conjecture that it was a feline canine tooth. 
Two small teeth (Plate 39, fig. 2, p 2 , p 3 ) are wedged in between the foremost 
tooth, i 1 , and the carnassial, p 4. 
In Phalangista vulpina one such tooth follows the front incisor; in Thai. Cookii 
there are two ; in Petaurus there are three denticles between the incisor, i 1 , and the 
premolar, p 4. To two of such seemingly functionless teeth those marked p 2 and 
p 3, in Plate 39, fig. 2, and Plate 41, figs. 1 and 2, may be homologous. Their interest 
lies, as in their homotypes in the upper jaw, in the manifestation of a diprotodont 
dentition under its extreme functional modification in the great extinct Marsupial 
Carnivore. 
Two sockets, indicated by p 2 and p 3, in the fossil figured in Plate 12, figs. 2 and 3, 
(1871), but which might have lodged the two roots of a single tooth, are now 
demonstrated to have held two small close-set teeth, of which the hindmost is hidden 
from outer view by the forepart of the carnassial, p 4. The foremost, p 2, immediately 
following i 1 , is more than twice the size of p 3, and has a cuspidate crown (Plate 39, 
fig. 2); but it is a dwarf by the side of the laniariform tooth, i 1 . To former descrip¬ 
tions of this tooth there seems nothing to add to the present demonstration of its 
place in the dental series. 
The tooth, to 1 , succeeding the carnassial, repeats in general character that described 
