1915.] Matthew and Granger, Lower Eocene Wasatch and Wind River Faunas. 89. 
tetradactyl and digitigrade. Wortman, following Cope’s erroneous deter- 
mination of the humerus belonging to this species, regards it as penta- 
dactyl.”" This inference is now proven correct by the fore and hind feet of 
P. ossifraga herein described. The character is probably generic, although 
it remains inferential for the large P. gigantea. Dissacus navajovius on the 
other hand may have been tetradactyl. The limb and foot bones are in- 
completely known but indicate proportions much more slender and feet 
more compressed than in the large species. 
Pachyena gracilis sp. nov. 
Type, No. 15729 lower jaws; paratype No. 15729, teeth and part of skeleton: 
both from the Gray Bull beds of the Big Horn Basin, Wyoming. | 
Distinctive characters: Total length of jaw = 244 mm.; canines and condyle 
much smaller, cheek teeth somewhat smaller and less robust than in P. ossifraga. 
Skeleton one-fourth smaller throughout, limbs somewhat more slender. 
The most obvious difference from P. ossifraga lies in the much smaller 
jaw, scarcely two-thirds the length of Cope’s species, with relatively thin 
and shallow ramus, short symphysis, small and slender canines, and small 
condyles. The cheek teeth are little less in length, but they are more com- 
pressed, with less robust cusps. ‘The paratype shows the limbs and feet to 
be smaller than in P. ossifraga, and somewhat more slender; the feet do not, 
however, attain the slender proportions of Mesonyx but are more like Synop- 
lotherium. ‘The astragalus is like that of P. osszfraga, slightly wider and 
shorter necked. Metacarpal II and metatarsal II are like those of P. 
ossifraga, and indicate that both pollex and hallux were reduced to small 
vestigial nodules. 
Measurements of P. gracilis. 
No. 15728 
Lower jaw, meisive alveolus to condyles: =. 2.0.5 6..0.5 2.20... 244 
GRO bose, eo PURO MGS s Souad ee Re ek | 32 
if 3 DPR Sak Cases CARR. Ee ATES RS REND SRT oe ae 36 
sf f Temertla of death, lige fis oe Ee a See 155 
is " i " TN 5g ars epee Pe Nee LS sg BV ana et aha hee Bk tS. Cal 132 
as as ig um LOG RIG YAM Sotbee eniiceneaen Fatal Cl UMmeERu mt ny AAC ian ane ante sor eae Mee c rr tae 60 
P; diameters hs Wear, ce hee ee a ie te eRe a iF OW tere, Gat ames’ 
P; ne REA es ox; PT NST RUE? MAURICE EN, ates AUER 19.3 X 8.4 
M, i CORON Nr oat ta tc Lg ae anaeS,  CaAkek re 19.8 X 8.8 
M, gy Joa) FAIR ai Ty SUD NCR HR SORENESS fo AR Cee Bey 213K OS 
: ? 
M ut US dicy Py 6th Rasa ge Onde Mai te ig Ga ahs aa Parte 200 7 
Net No. 15729 
Upper canines, tenet det 8000) Fess to ee a is 82.5 
e bh ae a em Gea ee Oe UIE ag Ve? ON aig Nina w tna ge: wk Ss 1 ee ie aa by Beg 
eae 
1Mem. Am. Mus. Nat. Hist., Vol. VI, p. 491. 
