1895.] Geology and Paleontology. 1087 
The Lower Jaw. 
Distance from front of symphisis to anterior border of 
ascending rami, . ‘ ‘ : i 3 . ; 385 
Depth of ramus below pm. ;, . : : Š ; ; 63 
Depth of ramus below m. „ . $ ‘ ; ; i 110 
Length of symphisis, : i : i i ae 152 
Length of diastema, : s ‘ ; ; : i 26 
Distance from base of pm. , to anterior mental foramen, 42 
The Dentition. 
Length of crowns of sup. internal, lateral incisors, . è 10 
Length of crowns of sup. median incisors, 7 ` 13 
Length of crowns of sup. external, lateral incisors, . ' 21 
Transverse diameter of sup. canine at base, . ; s 26 
Length of inf. premolar-molar dentitions, ; . F 310 
Length of inf. premolar dentition, . ; > : : 107 
Length of inf. molar dentition, ‘ $ : hiss Ae 
The Phylogeny of Diplacodon. 
Marsh, Osborn’ and Earle‘ have all agreed in considering Diplaco- 
don as ancestral to Titanotherium, and the present material only em- 
phasizes the correctness of their views. This is evidenced not only by 
the structure of the teeth which, as was first pointed out by Marsh, is 
intermediate between Paleosyops and Titanotherium, but also by the 
general appearance of the skull which is strikingly like that of the 
latter genus, as will be seen by referring to the figures in Plates 
XXXVIII and XXXIX. This likeness is shown in the great depth 
of the cranium above the premolars and molars, in the absence of a 
sagittal crest, presence, shape and position of the horns, breadth of 
nasais, etc. 
Earle, in his very excellent memoir on Paleosyops just cited, has 
attempted to indicate the phylogenetic positions of the various genera 
and species of the earlier Titanotheres. In this paper he derives 
Diplacodon from Telmatotherium. Later, Osborn,’ in describing two 
2 New Tertiary Mammals, Am. Jour. Sci. & Arts, March, 1875, p. 246-247. 
3 The Mammalia of the Uinta Formation. Trans. Amer. Phil. Soc., Vol. XVI, 
pp. 461-572. 
+A Memoir upon the Genus Paleosyops Leidy, and its Allies. Jour. Acad. 
Nat. Sci. Phil., Vol. IX, pp. 267-388. 
5 Fossil Nandi of the Uinta Basin. Expedition of 1894. Bull. Amer. Mus. 
Natl. Hist., Vol. VII, pp. 71-105. 
