34 FOSSIL MAMMALIA OF THE 



the crown is triangular, with tlie base turned outwards, and the apex formed by the antero- 

 internal lobe : the anterior half of the base projects more outward than the posterior half. 



Of the six molars in sitii showing the type above defined, the crowns increase in size 

 from the first (//« i) to the third {in. 3) and decrease from the fourth to the sixth {m 6), 

 which seems to be the least of all. Of this tooth the outer side is turned obliquely 

 backward, the low j)osterior portion of that side being much curtailed : thus the fore- 

 and-aft dimension of m 6 is less than that of the antecedent molars. Moreover, the outer 

 surface of the maxillary runs inward behind the sixth molar without appearance of 

 fracture, and confirms the ascription of six molars, and not more, to the series on each 

 side of the upper jaw. 



The Mammal indicated by the present specimen is nearly allied to Amblofhenum. It 

 belongs, however, to a distinct genus, here represented by a species as large as Jmb. musle- 

 liila. In extending the comparison to other genera known by the upper as well as the 

 lower teeth, Stylodon alone arrests attention. But, besides the differences in the number 

 of molars behind the long-crowned premolar, there are differences of configuration of the 

 grinding-surface of the molar teeth, as compared with the fossil ui)per jaw (PI. II, fig. 14, 

 ey.). True it is that this unique example presents the inner side of the maxillary teeth 

 to view : but, though there be some increase of fore-and-aft breadth as the crown extends 

 oiitAvard, there is no accessory cusp in the molars of that specimen, answering to the one 

 marked d, which is plainly shown at the middle of the hinder border of the crown in the 

 molars of fig. 3 -. the fore-and-aft extent of the outer part of the crown in fig. 3 is relatively 

 greater than in fig. 14. 



The last premolar m Peralestes, with a fore-and-aft breadth not exceeding that of m 1, 

 has a crown of twice the length. It is a long, sharp cone, and answers serially to the 

 inner one in the trae molars. A ' cingulum ' is indicated along the outer side of the base 

 of the cone [p, fig. 3 a) and develops a minute cusp both before and behind that base, 

 or at least behind it. The front talon may be described as a mere thickening there of the 

 cingulum. The outer tubercular wall of the crown in the succeeding teeth seems to be a 

 development of the cingulum. This premolar, like the succeeding molars, shows two 

 external roots, the front one being the largest. The seven teeth are close-set. 



An upper strip of the maxillary, in advance of these teeth, indicates a long and slender- 

 snouted form of head, recalling that in lS[ijrmccobius and Peramelcs. 



SarcophUus urshnis comes nearest in the character of its upper molars to the present 

 species of Peralestes. The outer part of the crown (ib., fig. 3 c) is low in proportion to its 

 fore-and-aft extent. It develops anteriorly a cusp, a, similar in its proportions and jjosition 

 to a in m 3 and vi 4, a. The hinder tract of the outer part in the second true molar of 

 SarcophUus develops two cusps, the larger of which answers to d in fig. 3 b. The inner 

 cusp (c) is the longest and sharpest cusp in both SarcophUus anA Peralestes. The ground- 

 work pattern is the same, with a generic distinction indicated by the accessory low inner 

 basal tubercle, and also by the minor number of molars in the large existing typodeutate 

 zoophiigous Marsupial. 



