170 



the merycoidodontim: 



The supraorbitals are much 



Foramina: The infraorbitals lie above the anterior part of M 2 . 

 closer to the median line than in P. altiramus. 



Dentition: The upper teeth appear to be typical of the genus, but those of the holotype are so 

 badly worn that their patterns cannot be discerned. The typical hypsodonty is present, and the teeth 

 are crowded, with P 1 set obliquely and outwardly overlapping on P 2 . In the lower jaw Ii seems to 

 have been lacking. All the other teeth were crowded, so that P 2 is situated partly inwardly and 

 partly posteriorly to Pi (the caniniform premolar). 



Fie. 123. — Pronomotherium siouense Sinclair. Right mandible. HT. 



(After Sinclair, 1915.) 



Cat. No. 12057 P.U.M. 1/2 nat. size. 



Discussion: Matthew (1924A) briefly described a number of upper and lower jaws from 

 Stonehouse Draw, Channel Quarry, Nebraska, found in the Sheep Creek, Horizon A beds (middle 

 Miocene). He considered these to be a variant of P. siouense and selected Cat. No. 18344 

 A.M.N.H., a mandible, as the type. He said that the size is a little larger throughout, the pre- 

 molars, especially the anterior ones, being proportionately larger and more robust but not showing 

 any clearly distinctive construction. 



This middle Miocene form may be annectent with Merycochoerus and, if so, should have a 

 name, probably as a subspecies under P. siouense, but the evidence in hand upon which to base a new 

 form is too scanty. 



Simpson (1932, p. 34) mentions "an upper canine of a fairly large oreodont, about the size of 

 Pronomotherium siouense. The root is less curved than is usual in this family." This specimen was 

 collected in the Midway formation (middle Miocene) of Florida, but I greatly doubt its reference to 

 this genus and species, as well as to the family. I believe the tooth should be referred to the Suida2. 



Pronomotherium species Gazin 1932 



Original Reference: A Miocene mammalian fauna from southeastern Oregon. Carnegie Inst. Wash. 

 Publ. No. 418, pp. 81-82, fig. 15a (Ticholeptus ? sp.). 



Locality: Twenty-eight miles south of Harper, Malheur County, Oregon, and approximately three miles 

 northwest of Skull Spring. 



Geologic Horizon: Upper Miocene (Skull Spring), or possibly lower Miocene. 



Material: Cat. No. 387 U.C.M., isolated P 3 in fragment of mandible. 



