13G 



where it forms that part of the floor of the nostril, n' ; and it is also grooved or chan- 

 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 XVI., 

 and the suture (s, with the maxillary has the same crenate character and course. 



The outlet of the socket of the first incisor is 9 1 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, is) 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, 4^ 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 Thylatinus. Besides this contribution to the third 

 socket, the portion of maxillary of Thylacoleo 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 & 2>, 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 Plate XL & Plate XIV. 

 fig. 1 is preserved in the present portion of the upper jaw ; but this satisfactorily demon- 

 strates the rest of the dentition of its side of that jaw, as respects size, kind, and number 



