36 



set closer together thai) in AmblotAerium, and the foremost is relatively larger. The crown 

 of the canine (c) rises vertically, with a slight backward curve to its sharp summit. It is 

 relatively narrower, antero-posteriorly, at its base than in Myrmecobim. It shows a well- 

 marked longitudinal groove at the inner side of its basal half near the hind border. It is 

 relatively longer and larger than in Amblotherium. 



The tirst premolar {/> i) is minute, with a low indication of one main cone and a hind 

 basal production : it stands distant by more than twice its own fore-and-aft breadth from 

 the canine. The second premolar (p 2) is one third larger than the first, with its main 

 cone and hind talon better marked: it stands half its breadth distant from the first. The 

 third premolar (p 3) is twice the size of the second; its main cusp is large and lofty; the 

 basal talon relatively low and small: it rises a little further from the second than does 

 that behind the first. The fourth premolar (p 4) increases chiefly in vertical extent; its 

 main cone is along subcompressed piercer; the hind talon is feebly marked : it stands 

 at the same distance from the third as that tooth does from the second premolar. 



The bases of the five succeeding teeth indicate a more complex type of crown. An 

 anterior as well as a posterior basal cusp is marked off from the main cone, and the ante- 

 rior cusp is larger and higher than the posterior one. One may infer the main cone from 

 the preserved impressions of the last three molars to have been long and slender ; it rises 

 chiefly from the outer side of the crown. Supposing each tooth preserved or indicated 

 in this portion of mandible to have worked upon a maxillary fellow, its generic distinction 

 from Peralestea would be established, and the dental formula of Phascolestes would be, 

 ' j j c —\ P 4_i m §=8 = 68, being four more than in Amphitherium, and fourteen more than 

 Mi/niiccobius. But, by the analogy of the latter genus, as above remarked, the number 

 of the molar series may have been less in the upper jaw. The lower contour of so much 

 of the ramus as is preserved in the subject of fig. 4, PI. II, is gently convex, curving 

 gradually up to the incisive areolar border. The symphysial articulation is long and 

 narrow. There is a feeble indication of the notch which is present at the anterior border 

 of the symphysis in Myrmecobim (PI. I, fig. 24), and is conspicuous in Amphitherium 

 Broderipii (ib., fig. 25). The anterior terminations of the linear groove near the lower 

 margin of the ramus, shown in the inner side of most of these small mesozoic mammalian 

 jaws, is here also visible. A fine line is continued from it to the lower end of the 

 symphysis. 



Incerta sedis. Peralestes, sp. ? 



In the proportion of depth to length of jaw the fragment of the right ramus (PI. I, 

 fig. 40 and 40 a), figured in my original memoir on Spalacotherium} and referred to that 

 genus, more resembles the present. Seeing, also, that the fore part of the ramus has 

 been broken off' behind the long symphysial articular surface, one might hazard a sup- 

 position that the teeth, there referred to a canine and anterior premolar, might be the 



1 ' Quart. Journ. Geol. Soc.,' vol. x, p. 431, fig. 12. 



