LAMBDOTHEEIUM. 709 



Found by the writer on a bluff on Green River, near the mouth of the 

 Big Sandy Creek, Wyomino-. 



LAMBDOTHERIUM Cope. 



AiDerieaii Naturalist, 1880, p. 74S, September 20. Bulletiu U. S. Geological Survey Terrs., VI, 1S81, p. 

 19(>. (?) Helolheriiim Cope, Pal;eoutolngical Bulletin No. 2, p. 1, August 3, 1-72. Proceediugs 

 Araericau Phiiosopb. Society, 1872, p. 4lJti. (Xoinen jiHdiim.) 



This genus is as yet only known to me from teetli of both jaws and 

 from mandibular rami. The dentition is much as in Limiiohjiis, excepting 

 that there is a diastema in front of the second inferior premolar. Presence 

 of first inferior premolar not ascertained. Fourth inferior premolar with- 

 out posterior cusps. Superior molars with an angular ridge extending 

 inwards from each inner cusp. Last inferior molar with heel or fifth lobe. 



The inferior molars in this genus are quite as in the other genera of 

 this family, while the superior molars show a tendency to Anchitliermm in 

 the well-defined tubercle and low crest extending outwards and forwards 

 from the internal tubercles. The external Vs are separated b}* a strong 

 rib. The internal cusp of the superior premolars is simple, and the external 

 cusps are well distinguished. 



If the ridges, which are rudimental in the molars of Hi/racotherium, 

 should be developed, and the external cusps of the superior molars be flat- 

 tened externally, the result would be the dentition of Lamhdotherium. 



I am acquainted with three species of Lamhdothermm, which differ 

 materially in size. The larger two are from the Wind River Eocene; the 

 smallest is from the Brido-er. 



^b^ 



Lambdotherium brownianum Cope. 



BiUletin U. S. Geological Survey Terrs., VI, 1S81, p. 196. 

 PlatoLVIa; fig. 10. 



Considerably larger than the L. popoariicum, and about equal to the 

 Tajnrus terrestris. The greater part of a lower jaw represents the species, 

 and on this unfoi*tunately only one of the premolar teeth remains. The 

 three premolars are all two-rooted, and the posterior lobe of the last true 

 molar is well developed. The inferior part of the external side of the 

 ramus contracts or retreats rather abruptly posteriorly below the last molar. 

 It presents a slight external convexity below the second and third premolars. 



