EVOLUTION OP THE SKULL AND TEETH OF EOCENE TITANOTHERES 



291 



Eotitanops gregoryi Osborn 



Plate LIV; text figures 25, 27, 33, 142, 143, 231, 245-247, 

 253, 483, 492, 493, 503, 661, 726, 727, 742 

 [For original description and type references see p. 192] 



Type locality and geologic Jiorizon.- — Alkali Creek, 

 Buck Spring, Wind River Basin, Wyo.; Wind River 



This very sharply defined species is named in honor 

 of Dr. William K. Gregory. Its especial interest lies 

 in the fact that it is the most primitive titanothere 

 known. It represents, however, a persistent primitive 

 stage, because its geologic level, 100 feet above the 

 alkali "red stratum," is higher than that of the 



Figure 245. — Model of skuU of Eotitanops gregoryi 

 Based on type specimen (Am. Mus. 14889) and on Eotiiamps iorealis. One-half natural size. 



formation, Lambdotherium zone, horizon Wind River B 



("Lost Cabin"), 100 feet above heavy "red stratum." 



Specific characters. — -Very primitive and of inferior 



size, p2-m3, 78.4 millimeters; mi_3, 49; P2-3 with the I (See fig. 246.) 



typical and relatively progressive E. borealis. Its 

 primitive condition is apparent in the comparison of 

 P3 with the same tooth in E. borealis and E. princeps. 



FiGTJBE 246. — Lower premolars and molars of Eotitanops 



Natural size. American iVEuseum specimens from the Wind River formation. Wind River Basin. A, B, C, Inner side view of the 

 third left lower premolar: A, E. gregoryi, No. 14889 (type), Alkali Creek, Buck Spring, upper level of "Big Red Pocket," 100 

 feet above heavy red stratum; B, E. iorealis, No. 14888, Alkali Creek Davis's ranch; C, E. princeps, No. 296 (type). D, E. gregoryi, 

 No. 14889 (type), left lower premolars (p2, ps), inner side view. E, E. brownianus. No. 4885 (type), second left lower premolar, 

 inner side view. F, E. borealis, No. 14891, west bank of Wind River, 3 miles above canyon (top of banded beds); left lower 

 molars (mi, ma) , inner side view. 



internal cusps, paraconid and metaconid, consisting of 

 rectigradations in a most rudimentary stage; hypo- 

 conulid of m3 very small; m^ with a single internal 

 cone, no hypocone. 



This third inferior premolar, ps, is much less pro- 

 gressive than in E. princeps or even in Lambdotherium; 

 the other premolars are correspondingly primitive, p2 

 short, compressed, with a very rudimentary hypo- 



