216 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
nelled longitudinally at its under part, which channel (figs. 2 & 3, 22 ') gains breadth 
and depth as it passes backward ; but it is broken away after contributing an inch to 
the median palatal suture (ib. p). 
The facial plate of the premaxillary repeats the characters of that figured in Plate il 
P hilosophical Transactions, 1866, and the suture ( s , s') with the maxillary has the same 
crenate character and course. 
The outlet of the socket of the first incisor is 9-| lines in fore-and-aft diameter, 6 lines 
in transverse diameter; the outer wall is outwardly convex, the inner one straight. 
The depth of the socket is 1^ inch ; it contracts to the closed end. The outlet of the 
second socket (fig. 3, i 2 ) is circular and small, 4^ lines in diameter ; it is also shallow, 
rapidly contracting to the closed end. 
The outlet of the third socket (figs. 2, 3, c) is larger, deeper, and elliptical, lines in long 
(fore-and-aft) diameter, 4 lines in transverse diameter ; it is separated by a diastema of 
two lines and more from the second, and its hind wall is formed by the maxillary ( 21 ), the 
proportion being the same as that which the maxillary contributes to the premaxillary 
for the lodgment of the canine in Thylacinus. Besides this contribution to the third 
socket, the portion of maxillary of Tliylacoleo here preserved shows three sockets of 
small tubercular premolars (ib. p 1 , 2 , 3 ) and the major part of that of the great carnassial 
tooth (ib. p 4). 
A portion of the outer alveolar plate (figs. 1 & 5, 21 ) is preserved, and also a portion 
of the palatal plate (figs. 2 & 3, 21 ), showing its concavity near the carnassial. 
The socket succeeding the third ( c ) is on the inner side of the hind or maxillary part 
of that socket, showing that the tooth it contained (figs. 2 & 3, p 1 ) held the same rela- 
tive position to the third tooth (ib. c) as does the anterior premolar to the canine in 
Lutra ; thus adding another to the extremely few instances simulating, in Mammalia , 
the double row seen in certain lower Reptiles and Fishes. The outlet of this socket 
is subcircular, 4 lines by 3^ lines, and is 3 lines distant from the outer surface of the 
maxillary. 
The next (fifth) socket ( p 2 ) is nearer the outer border of the alveolar process, one 
line and a half behind the back part of the third socket ; it is circular, three lines in 
diameter. It is immediately succeeded by a sixth socket ( p 3) of similar size and shape, 
situated more outwardly as well as posteriorly, the alveolar wall curving from the pre- 
maxillo-maxillary suture outward and backward to the prominent fore part of the socket 
of the great carnassial ( p 4). 
This socket extends backward almost at a right angle with those of the three small 
antecedent teeth (fig. 3) ; its length from before backward is 2 inches 1 line ; its greatest 
breadth near the fore part is 7 lines. 
No part of the socket of the small tubercular molar shown in Plates xi. & xiv. fig. 1 
of the Philosophical Transactions, 1859, is preserved in the present portion of the upper 
jaw; but this satisfactorily demonstrates the rest of the dentition of its side of that jaw, 
as respects size, kind, and number of teeth, and thus supplies what was less perfectly 
