Peterson: Material Discovered in Uinta Basin. 125 



Uinta tapir. The last lower molar has also a very large third lobe. 

 Some of the characters above adduced as to the teeth of Isectolophus 

 annectens may show by later discoveries that this species is not in the 

 direct line leading to the true tapir." On page i8o of the same pub- 

 lication is found, by the same authors, the following: "In fact all the 

 known species of both Systemodon [Ilomogalax] and Ileplodon are 

 extremely slender forms, as compared with their supposed Miocene 

 [= Oligocene] successors, and if we derive the true tapirs and pseudo- 

 tapirs from any of the known species of either of these genera we must 

 suppose a considerable modification of their foot-structure to reach 

 the condition found in their Miocene [= Oligocene] relatives. The 

 dentition of these early Wasatch and Wind River Tapiroids, however, 

 is well adapted for further evolution into later Miocene [= Oligocene] 

 types, but in their foot-structure we find it otherwise." 



Mr. Hatcher objects to regarding Isectolophus as the ancestor of the 

 tapirs as follows: (/. c, p. 178) "Themetacone \n Protapiriis is placed 

 farther in, and is less prominent and not so convex externally as in 

 Isectolophus, while the same element in recent Tapirs is more prominent 

 and has a more external position than in Isectolophus. Thus, accord- 

 ing to our present phylogenetic arrangement we should have to allow 

 for first a gradual shifting inward of the position of this cone followed 

 by a period when it commenced to move outward to its normal position 

 in modern Tapirs, a rather extreme case of oscillation, but not entirely 

 inconsistent with what Scott has shown to have taken place in the 

 equine series." 



If we accept the phyletic development of the superior premolar den- 

 tition of the three Oligocene species of Protapirus,^°^ namely, P. 

 simplex, P. validus, and P. obliquidens, as well-established, we have 

 not yet, to my mind, established any satisfactory evidence that there 

 has been found in the American Eocene an ancestor for these forms. 

 In Helaletes the deuterocone of P- is already slightly divided at the 

 apex, while in Isectolophus and Parisectolophiis there are two distinct 

 internal tubercles. On the other hand the upper premolars of Pro- 

 tapiriis simplex, a much later form of the Oligocene, has only one inter- 

 nal cone, the paraconule of P- being even less developed than in 

 Ilomogalax from the Big Horn Eocene. From the comparative char- 



1"^ Hatcher, J. B., Amer. Jour. Set., Vol. I, 1896, p. 179. (Hatcher questions the 

 propriety of referring the American species of the Ohgocene tapiroids to the Eur- 

 opean genus Prolapirus.) 



