46 Bulletin American Museum of Natural History. [Vol. XXXIV, 
Key to Genera of Oxyenide. 
A. Two subequal shearing molars, m; and m3; p= without internal cusp or root; 
m? transverse, unreduced. 
1 VES pirement, Cael OF PRRBIAN a cous vise bee re eee Prolimnocyon. 
2. M8 absent, astragalar trochlea flat.............0...0.00 00. Dipsalidictis. 
3. M$ absent, astragalar toa ok BPORVOR od 6 Thinocyon, Limnocyon. 
B. M2 as large or larger than m,; p® with internal root and usually cusp. 
4, M2 transverse; mp, with distinct metaconid and heel.......... Oxyena. 
5. M2 absent; m». with vestigial metaconid and heel............. Patriofelis. 
C. My smaller than m; p® with internal cusp. 
6. M2 small, not transverse; metaconid on mg............... Paleonictis. 
7. M2 small, transverse; no metaconid on mg............. Ambloctonus. 
Oxyena Cope 1874.' 
Type, O. lupina from Wasatch of New Mexico. 
The types of the three species described by Cope are from New Mexico, 
where the genus is fairly common. A number of topotypes obtained by 
Mr. Granger in 1912-13 serve to check the validity of these species and to 
compare them with the more numerous and better preserved specimens 
secured in the Big Horn Valley. The genus occurs also in the Lost Cabin 
stage represented by more progressive and larger species, and in the Clark 
Fork and Sand Coulée horizons is represented by more primitive species. 
The progressive characters of Oxyena are toward a higher predaceous 
specialization. The carnassial teeth mz develop a more perfect shear on 
the trigon and the metaconid and heel of m, tend to disappearance. The 
earlier species are more like Limnocyon and Paleonictis in various respects, 
and the divergence between the three phyla becomes emphasized later on. 
The geological horizon of the species of Oxyena from first to last is in exact 
accord with their progressiveness. 
Key to Species of Oxyena. 
i M, = Ms 
A. ‘Trigonid of m, broader than long, heel large. 
BR OR YE REGS re fMRI E AE: Bee WA OREN BP ONT O. equidens. 
II. My, smaller than mg, 
B. ‘Trigonid of m, slightly broader than long, heel large. 
2. 7a ems, nie wenhO “anti i. Selsey Sane et O. transiens. 
C. Trigonid of m; somewhat longer than broad, heel moderate. 
3. Size small medium, pi-m, = 65-70... 0.2... cee eee O. gulo. 
4. Sizeclarge, pi-Ms = BO-85° mm... ee ek de ek O. forcipata. 
D. Trigonid of mz considerably longer than broad, heel small. 
5. Size medium 
6. Size largest. Molar teeth insufficiently known 
1 Cope, 1874, Rep. Vert. Fors. New Mex., p. ak 
