1 2 SCOTT. [Vol. V. 



a trace on m. 3, and none on the others, while a third specimen 

 is entirely devoid of them. 



B. Lower Jaw. — The incisors are small, and have simple, 

 compressed crowns, very different from the curious, shovel-like 

 teeth of existing species. They differ also from the latter in 

 relative size, the median incisor being the smallest and the 

 external the largest of the series. In position they are quite 

 strongly procumbent. The canine, in all the specimens which 

 I have seen, is very small, though larger than the incisors ; it is 

 more erect than the latter, and has a very much compressed 

 crown, the anterior and posterior edges of which meet at nearly 

 a right angle. The first premolar, as in the upper jaw, stands 

 isolated, both from the canine and from pm. 2 ; it is implanted 

 by a single stout fang, and has a very small simple crown. The 

 other premolars increase in size from pm. 2 to 4, and are all 

 much alike, have elongate and very much compressed crowns, 

 with an acute apex and trenchant edges ; each has a distinct 

 anterior basal cusp, and on pm. 3 and 4 there is an internal 

 ridge which runs backwards from the median apex. This is 

 barely indicated on pm. 3, but is well shown in 4, and in some 

 specimens encloses a distinct " lake " with the external wall ; in 

 others it is open internally. The molars are elongate but very 

 narrow, and show a distinct tendency toward hypsodonty ; the 

 valleys are very narrow, but perfectly simple, and not compli- 

 cated by any projections from the walls ; the internal faces are 

 much flattened, and there are no pillars or anterior " compres- 

 sion-folds," which are so conspicuous in AucJienia. The fifth 

 crescent of m. 3 varies very much in size, being nearly twice as 

 large in some specimens as in others. Basal pillars are much 

 less frequent than in the upper molars. I have seen them in 

 but one specimen, and then as a mere rudiment on m. 1. 



The chief peculiarity of the dentition of Pcebrotherium con- 

 sists in the very elongate, simple, and trenchant premolars 

 which recall those of Xiphodon rather than those of any existing 

 ruminant. 



The Milk Dentition. — I have not been able to determine 

 whether the first premolar has a predecessor or not ; at all 

 events, the tooth which represents it in the temporary series is 

 of similar size and constitution. The second upper milk-molar 

 (D- 2) is like its successor pm. 2 in the permanent set, but the 



