1915.] Matthew and Granger, Lower Eocene Wasatch and Wind River Faunas. 479 
(= Daubentonia), is the only objection to this reference. The central pair 
of incisors are slightly enlarged in Omomys and Hemiacodon, and in Tetonius 
the front tooth is very considerably, but not comparably to this genus. The 
enlarged front tooth is not well shown in my photographs of the type speci- 
men although sufficiently noticed in the description, and Doctor Schlosser 
apparently failed to observe it, as he does not refer to it in defining the genus, 
and his definition of the family specifies “incisors and canines normal but 
the latter small.” 
Phenacolemur gen. nov. 
Type, P. precox infra. ; 
Generic characters: Dentition 1.0.1.3. Incisors enlarged procumbent, long- 
rooted, with long pincer-like crown. Py, large, moderately compressed, simple with 
small heel. Molars with low trigonid and basined heel, no paraconids, m; and mz 
with two pairs of equal well separated cusps, m3; with three pairs; a tendency to a 
transverse crest between each pair of cusps. Posterior mental foramen beneath m). 
This singular little genus is represented by about a dozen specimens of 
lower jaws, pertaining to two or more species all from the Gray Bull and Sand 
Coulée horizons. The molars and premolars are widely different from those 
of Trogolemur, but Apatemys of the Bridger is to some extent intermediate. 
In Apatemys ps is reduced, almost vestigial; in this genus it is enlarged; the 
heel of m3 in Apatemys is long with a single hypoconulid instead of the pair of 
cusps in Phenacolemur; m,-2 in Apatemys are shorter, wider and of more ovate 
outline, with the usual trigonid and heel as in Tarsiide. The upper molars 
referred to Phenacolemur are superficially very like those of Paramys. But 
the construction differs in detail, and the base of the zygomatic arch has the 
normal Primate or Insectivore position, instead of the anterior position 
characteristic of Paramys and all rodents. The front of the lower jaw is 
equally rodent-like, but the molars are of the normal tritubercular construc- 
tion, and the incisor is rooted, the crown enamelled on both sides, and not 
scalpriform. The genus might be regarded as an ancestral stage in the 
evolution of simplicidentate rodents, but is too imperfectly known for such 
a speculation to have any value. It cannot be genetically ancestral, as it 
is a contemporary of Paramys in which the subordinal characters are fully 
developed. 
Phenacolemur precox sp. nov. 
Type, No. 16102, lower jaw, from Sand Coulée beds of Clark Fork basin, Wyoming. 
Specific characlers: Ps-m2 = 13.8 mm.; molars broader and more robust. : 
The type has ps-mz complete, crowns of the last molar and incisor broken off. 
P, has a short, broad heel, but no anterior basal cusp or ridge. My and m: have a 
