NO. 8 UPPER EOCENE ARTIODACTYLA — GAZIN 35 



Uinta C sequence than the Protylopus annectens quarry in Myton 

 pocket, has produced, if not always smaller-, essentially narrower- 

 toothed forms. About 90 percent of the Pentacemylns material from 

 Leota quarry is P. leotensis, perhaps all the Protoreodon material is P. 

 primus, and all the Leptotragulus specimens appear to be L. clarki. 

 At Myton pocket all the pentacemylids are P. progressus, the equiva- 

 lent large protoreodont is P. pumilus annectens, and about 85 percent 

 of the Leptotragulus specimens are L. medius. It is highly improbable 

 that the difference in each case is to be accounted for by dimorphism 

 within a species. Moreover, the localities are less than 20 miles apart, 

 and both P. progressus and P. pumilus annectens noted above in the 

 Myton locality are recorded from the Randlett horizon, still later 

 than the Leota quarry. 



MYT0N0MERYX,i2 new genus 



Type. — Mytonomeryx scotti, new species. 



Generic characters. — Elongate rostrum with marked diastemata 

 separating the first and second premolars, above and below, from 

 adjacent teeth. M^ and M^ noticeably quadrate and both with a well- 

 developed hypocone. Upper molars moderately selenodont with 

 prominent mesostyle. 



Discussion. — Mytonomeryx resembles closely contemporary Penta- 

 cemylus in the progressiveness of its selenodont tooth structure over 

 that of earlier Bunomeryx, but differs strikingly from Pentacemylus 

 in retention of a prominent hypocone on both M^ and M^. In this 

 respect it differs also from Bunomeryx, which has nearly or quite 

 lost this cusp on M^. Retention of the hypocone is suggestive of 

 Hylomeryx, but in this stem there is a tendency toward the develop- 

 ment of a protoloph and the external styles are weak, with the meso- 

 style weak or absent. Mytonomeryx would appear to have derived 

 from the Pentacemylus line but separating from it earlier than the 

 Bunomeryx stage. 



MYTONOMERYX SC0TTI,i3 new species 

 Plates I, 2 (below), and 3, figure i 



Type. — Skull, jaws, and other skeletal portions, U.S.N.M. No. 

 20401. 



Horizon and locality. — Uinta C, Myton pocket, 7 miles east of 

 Myton, Duchesne County, Utah. 



12 From Myton, locality ; and Greek firjpv^, ruminant. 

 " Named for Prof. W. B. Scott. 



