﻿UESUS. 15 



teeth with low crowns and rather long cylindrical roots, pm. 1 being the largest 

 and the one which most commonly persists. 



Pm. 4 is a small tooth showing much variation. As a rule, in addition to the 

 principal cone, one or more of three little cusps may be developed, two placed 

 respectively at the antero -internal (PI. VI, fig. 0, 1) and postero-internal (PI. VI, 

 fig. 6, 3) edges, and the third (PL VI, fig. 6, 2) slightly behind and to the inner side 

 of the principal cone. 



In bears of the arctos type the development of inner cusps is not so great as 

 in the cave bear, and in many cases the tooth is entirely without them. 



M 1. This is an elongated tooth, divided by a constriction into a posterior 

 square portion (g) whose length is about one third of that of the entire tooth, and 

 an anterior more elongated portion. The posterior portion, which represents the 

 greatly enlarged heel or talon of the corresponding tooth in Canis, has the surface 

 raised into a series of low cusps, the two most marked of which lie on the inner 

 border and are nearly equal in size. The anterior portion generally shows two 

 prominent cusps, one forming the anterior extremity of the crown, one farther 

 back and on the outer side of the tooth. There are several smaller and generally 

 ill-defined cusps along the inner border. Each portion of the tooth is supported 

 by a strong root. The angle of divergence between the two roots varies much. 



In bears of the arctos type the constriction between the two portions of the 

 tooth is not so marked as in the cave bear, and the cusps are less prominent. The 

 hinder of the two, lying on the inner border of the posterior square portion of the 

 tooth, tends to be larger than the anterior. The cusp forming the anterior end of 

 the tooth is less marked than in the cave bear, and often has a small accessory 

 cusp on its inner side. 



M. 2. The sides of this tooth are parallel, and the length is nearly twice the 

 breadth. A slight constriction divides the tooth into anterior and posterior halves. 

 The surface is somewhat uniformly tuberculated, the greatest elevation lying 

 antero- internally. The tooth is fixed in the jaw by two stout roots, the posterior 

 being the larger. 



I cannot detect any difference from the above in teeth of bears of the arctos 



typ e- 



M. 3. The crown, which has parallel sides, is slightly rounded in front and 

 more markedly rounded behind. The length as compared with the breadth is about 

 5 — I. The posterior border is sometimes rounded, sometimes more or less 

 obliquely truncated externally. The surface of the crown is very uniformly covered 

 with low tubercles (PI. VI, fig. 5), the largest being placed at the antero internal 

 angle. There are three roots, one placed anteriorly and two posteriorly, but all 

 three roots sometimes coalesce. 



In bears of the arctos type the tooth is rather longer in proportion to its width 



