198 



Annals of the Carnegie Museum. 



and is nearer to the base of the antler. Above the burr the surface 

 is much roughened. 



PROBOSCIDEA. 



Mastodon. 

 No. 785- 

 In the collection from Loup Fork beds of the Madison valley is 

 the mandible of a young mastodon, which is of interest on account 

 of its possessing the milk dentition. On one 

 side the first premolar is present. It is a small 

 tooth, only a fraction of the size of the suc- 

 ceeding one. It is elliptical in section, be- 

 ing longer than wide. The anterior portion 

 is conical. Back of this and separated by a 

 shallow transverse groove is a double heel or 

 perhaps a rudimentary cross-crest, which by 

 another slight groove is divided on top into 

 two lateral tubercles, the outer one being the 

 larger, dp^- is worn on the grinding surface. 

 There were two principal cross-crests : the 

 posterior ones are the larger, and the outer 

 portion of the latter is much larger than the 

 inner portion. Three small circular spots where 

 the enamel is worn through indicate three 

 tubercles on the anterior portion of the tooth. 

 There was also a posterior median tubercle 

 behind the posterior cross-crest, and on the out- 

 er side of this a smaller mammillary tubercle. 

 On P-g there are three principal cross-crests 

 with at least two anterior and two posterior 

 accessory ones. The principal cross-crests are 

 Fig t,-] Merycodiis? ^'fe'^ ^^^^ unworn, and each is composed of 

 (No. 804). Portion of two principal tubercles. The inner ones are 

 antler. Lower Madison the larger. Of the two posterior tubercles 

 valley. 3^ natural size. composing the heel the inner one is slightly 

 the larger. 

 P^ was still buried in the base of the ascending ramus back of P^, 

 showing the mode of succession to be just as in modern elephants. 

 It was composed of three principal high cross-crests each with two 

 cusps, as in P3 and the tooth was nearly of the same size. 



