DISCOVERY OF THE TITANOTHERES AND ORIGINAL DESCRIPTIONS 



169 



angular ridge extending inward from each inner cusp. Last 

 inferior molar with heel. * * * The V-shaped crests of the 

 inferior molars separate it from Hyracotherium. 



Etymology. — Xa/i/35a, lambda; dTjplov, beast; in allusion 

 to the A-shaped crests of the lower molars. 



Present determination. — The genus is valid and is 

 now referred to the Eocene titanotheres. 



Lambdotherium popoagicum Cope, 1880 



Cf. Lambdotherium popoagicum Cope, this monograph, page 281 



Original reference. — Am. Naturalist, vol. 14, pp. 

 746, 747, 1880 (Cope, 1880.1). 



Subsequent reference. — Tertiary Vertebrata, p. 710, 

 pi. 58b, figs. 7 and 7a, 1884 [1885] (Cope, 1885. 1). 



Type locality and geologic Tiorizon. — Badlands of 

 Wind Elver, western-central Wyoming; Lambdo- 

 iherium-Eotitanojps-Coryphodon zone (Wind River B). 



Type. — A lower jaw with dentition (Am. Mus. 4863). 

 (See fig. 103.) 



Specific cliaracters. — Cope writes : 



The heels of the second and third premolars have 

 a median keel; the third only has an anterior 

 tubercle. The crest of the heel of the fourth forms 

 an imperfect V. Heel of the last true molar small. 

 No cingula; enamel smooth. Length of molar series 

 80 [millimeters]; of true molars 44; of last molar 

 19; depth of ramus at first premolar 21; at last 

 molar 31. * * * About the size of Hyrachyus 

 agresiis. 



Etymology. — popoagicum, in allusion to 

 Popo Agie River, a tributary of Wind River. 



Present determination. — The species is 

 valid. (See p. 283.) 



Lambdotherium brownianum Cope, 1881 



Cf. EoHtanops brownianus (Cope), this monograph, 

 page 292 



Original reference. — U. S. Geol. and Geog. 

 Survey Terr. Bull., vol. 6, p. 196, 1881 

 (Cope, 1881.2). 



Subsequent reference. — Cope, Tertiary 

 Vertebrata, p. 709, pi. 56a, fig. 10 (not the 

 type), 1884 [1885] (Cope, 1885.1). 



Type locality and geologic horizon. — Badlands of 

 Wind River, western-central Wyoming; Lambdo- 

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



Holotype. — "The greater part of a lower jaw," 

 with p^, m'-m' (Cope collection. Am. Mus. 4885). 

 (See fig. 104.) 



Characters. — Cope writes: 



Considerably larger than the L. popoagicum and about 

 equal to the Tapirus ierreslris. The greater part of a lower 

 jaw represents the species, and on this, unfortunately, 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 e.xternal 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. The alveolar line rises rapidly 

 101959— 29— VOL 1 14 



posteriorly, so that the last true molar is quite oblique. The 

 second (first) premolar has a considerable heel, which is narrow 

 and elevated on the middle line. The principal cusp is large 

 and compressed but obtuse and has no anterior basal tubercle. 



Measurements [Cope] 



Millimeters 



Length of six molars 90 



Length of true molars 55 



Diameters of second (first) premolar: 



Vertical 9 



Anteroposterior 12 



Transverse 6 



Length of base of first true molar 15 



Width of base of first true molar 9 



Length of base of third true molar 23 



Width of base of third true molar 11 



Depth of ramus at second premolar 30 



Depth of ramus at ma: 



At front of tooth 39 



At end of tooth 47 



Etymology. — "Dedicated to my friend Arthur E. 

 Brown, superintendent of the Philadelphia Zoological 

 Garden" (Cope). 



FiGUEE 103. — T3'pe (holotype) of Lambdotherium popoagicum 

 Left mandibular ramus, with pj-ms. Am. Mus. 4863. After Cope, 1885. Natural size. 



Present determination. — The species is valid, 

 generic reference is to Eotitanops. (See p. 292.) 



The 



Palaeosyops hyognathus Osborn, 1889 



Cf. Dolichorhinus hyognathus (Osborn), this monograph, 

 page 409 



Original reference. — Am. Philos. Soc. Trans., new 

 ser., vol. 16, p. 513, 1890 [author's reprint issued 

 Aug. 20, 1889; O. P. Hay] (Scott and Osborn, 1890.51). 



Subsequent reference. — Earle, A memoir upon the 

 genus Palaeosyops Leidy and its allies: Acad. Nat. Sci. 

 Philadelphia Jour., 2d ser., vol. 9, pi. 11, figs. 10, 

 11 [type], 1892 (Earle, 1892.1). 



Type locality and geologic horizon. — Washaliie, White 

 River, northeastern Utah; Washakie B. 



