194 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Specific cJiaracters. — Osborn writes: 



Of superior size, Mts III 104 millimeters longitudinal, 16 

 transverse, index 15. 



This ill-defined species indicates the existence in Wind River 

 times of a relatively large, short-footed titanothere, v^hich is 



Figure 143. — Lower jaws of Lambdotherium and 

 EoHlanops 



A, Lambdothenum popoagicum; B, Eotitanops gregoryi (holotype); 

 C, Eoiiianops browniamis; D, Eotitanops boreatis; E, Eotitanops 

 princcps (type). .One-fourth natural size. After Osborn, 1913. 



possibly ancestral to some of the short-footed middle Eocene 

 types. The comparative measurements with the median 

 metatarsal of E. borealis are as follows: 



Etymology. — major, larger; in allusion to the supe- 

 rior size of this animal compared with others of the 

 same genus. 



Present determination. — A valid specific stage. 



Lambdotherium priscum Osborn, 1913 



Cf. Lambdotherium priscum, this monograph, page 286 



Original rejerence. — Am. Mus. Nat. Hist. Bull., vol. 

 32, pp. 413-414, figs. 7A, 9A, September 2, 1913 

 (Osborn, 1913.400). 



Type locality and geologic horizon. — -Wind River 

 Basin, 3 miles east of Lost Cabin, Wyo.; Lambdo- 

 therium-Eotitanops-Ooryphodon zone (Wind River B). 

 Granger, American Museum expedition, 1905. 



Type. — Am. Mus. 12822, anterior portion of jaw 

 with P2-P4, nil of right side, also ps, mi, m2 of left 

 side. Rami fragmentary. (See fig. 146.) 



Specific cJiaracters. — Osborn gives the following 

 description: 



P2-P4, 25 millimeters. Second and third lower premolars 

 extremely simple, with rudimentary paraconid. Metaconid 

 of p3 rudimentary, placed very low upon slope of protoconid; 

 talonid narrow, depressed, with cingular rudiment of entoconid. 



The extremely simple or primitive structure of the second 

 lower premolar clearly distinguishes this stage. 



A referred specimen (Am. Mus. 14908) is slightly more 

 advanced in the structure of the second lower premolar, but is 

 still much more primitive than the type of L. popoagicum. 



This specimen was found in the Wind River Basin, Dry 

 Muddy Creek, 18 miles up (Granger, Am. Mus. expedition, 

 1909). 



The measurements of these two specimens are: 



Type 

 (No. 12822) 



Mm. 



Second to fourth premolar, inclusive 25 



Third premolar, anteroposterior 8 



Third premolar, transverse 5 



Fourth premolar, anteroposterior 9 



Fourth premolar, transverse 6. 5 



First molar, anteroposterior 11.5 



First molar, transverse 7. 5 



First to third molar, inclusive 



Beferred 

 specimen 

 (No. 14908) 



10 



7 

 37 



Etymology. — priscus, ancient; in allusion to the 

 primitive character of the species. 



Present determination. — A valid specific stage. 



Lambdotherium progressum Osborn, 1913 



Cf. Lambdotherium progressum, this mongraph, page 286 



Original rejerence. — Am. Mus. Nat. Hist. Bull., 

 vol. 32, p. 415, fig. 8, September 2, 1913 (Osborn, 

 1913.400).- 



Type locality and geologic horizon. — Wind River 

 Basin, Wyo. (Alkali Creek, Buck Spring); Lambdo- 

 therium- Eotitanops- Cor yphodon zone (Wind River B). 

 Granger, American Museum expedition, 1909. 



