1915.) Matthew and Granger, Lower Eocene Wasatch and Wind River Faunas. 471 
characters in the molar teeth. They appear to be in genetic sequence, the 
stage of progress of each specimen being in exact correspondence with its 
recorded geological level. 
Key to Species of Cynodontomys. 
1. C. angustidens sp. nov. Ps-m; = 14 mm. PP, narrower, oval, with small heel 
and deuteroconid much smaller than protoconid. 
2. C.latidens Cope. Ps-m;=15mm. P,with deuteroconid distinctly smaller than 
protoconid, heel narrower than in C. scottianus, its cusps less separate. 
3. C. scottianus (Cope). Pse-m3; = 17.3 mm. P, with deuteroconid a little smaller 
than protoconid, and heel broad basined with hypoconid and entoconid wide 
apart. 
The geological occurrence is as follows: 
Bighorn Basin Wind R. Basin | Beaver Divide | Clark Fork Basin 
| ee | ———s | —___. 
Lost Cabin | C. scottianus C. seottianus | C. scottianus 
1 sp’m 17 sp’m’s 1 sp’m 
Lysite C. latidens C. latidens 
16 sp’m’s 2 sp’m’s 
Gray Bull »| C. angustidens C. angustidens 
9 sp’m’s 1 sp’m 
_ JT have not identified the genus with certainty from the New Mexican 
Wasatch, nor from the Clark Fork beds. A single specimen from the lowest 
Gray Bull level in Clark Fork basin appears to be a primitive mutant of C. 
angustidens. 
The Paleocene ancestors of Cynodontomys have not been found, or at all 
events have not been recognized as such. | 
Cynodontomys scottianus Cope. — 
Microsyops scottianus Corn, 1881, Bull. U. 8. G.S. Terrs., Vol. VI, p. 188; 1885, 
Tert. Vert., p. 217, pl. xxiva, fig. 2; Ossorn, 1902, Bull. Amer. Mus. Nat. Hist., 
Vol. XVI, p. 209, fig. 36. 
Type, No. 4748, left ramus of lower jaw with ps and alveoli or roots of remaining 
teeth. Wind River basin, Wyoming. Wortman, 1881. Probably Lost Cabin beds. 
Distinctive characters: Ps-ms3 = 16.8-17.8 mm. Py, less molariform than in 
Microsyops, more than in C. latidens. Ms unreduced. P3 two-rooted, obliquely 
set in type, usually straight. 
