166 



TITANOTHERES OF ANCIENT "WYOMING, DAKOTA, AND NEBRASKA 



Etymology. — 5t?, double; kcows, cone; because the 

 third upper molar had two mner cones. 



Present determination. — The name P. diaconus Cope 

 is probably a synonym of Palaeosyops rohustus 

 (Marsh), as explaiaed in Chapter V of this mono- 

 graph. 



Diplacodon Marsh, 1875 



Cf. Diplacodon Marsh, this monograph, pages 155, 439 



Original reference. — Am. Jour. Sci., 3d ser., vol. 9, p. 

 246, March, 1875, "dated February 20, 1875" (Marsh, 

 1875.1). 



Type species. — Diplacodon elatus Marsh. (See 

 p. 439.) 



Generic characters. — Marsh writes: 



The genus here established presents characters in some 

 respects intermediate between Limnohyus and Brontotherium. 

 It agrees with the former in its complete dentition (44 teeth) 

 and in the general form of the incisors, canines, and true molars. 

 It resembles the latter still more closely in the premolar and 

 molar teeth, and parts of the skeleton, especially in the verte- 

 brae, and bones of the extremities. From the Eocene Limno- 

 hyidae, already described, this genus is sharply distinguished 

 by the last upper premolar, which has two distinct inner cones, 

 thus agreeing essentially with the first true molar. This char- 

 acter, which has suggested the name of the genus, is one step 



^9 



Characters. — The specific characters were not for- 

 mally separated from the generic characters above 

 given under Diplacodon. 



Measurements [Marsh] 



Millimeters 



Extent of upper molar series 242 



Extent of upper true molars 152 



Anteroposterior diameter of last upper molar 60 



Transverse diameter 59 



Anteroposterior diameter of [upper] canine, at base 32 



Height of crown 27 



Etymology. — elatus, lofty; apparently in allusion 

 either to the large size or to the advanced stage of 

 evolution. 



Present determination. — This important genus and 

 species was based upon an excellent type. The genus 

 and species are vahd. (See p. 439.) 



Brachydiastematherium Bockh and Maty, 1876 



Cf. Brachydiastematherium Bockh and Maty, this monograph, 

 page 382 



Original reference — Mittheilungen aus Jahrb. K. k. 

 geol. Anstalt, Band 4, pp. 125-150, 1876 (1876.1). 



Type species. — Brachydiastematherium transilvani- 

 cum Bockh and Maty. (See p. 382.) 



Figure 



-Marsh's type of Diplacodon elatus 

 One-third natuial size. 



toward the modern type of perissodactyl dentition. The dental 

 formula of the genus is the same as Limnohyus, viz, incisors f , 

 canines \, premolars |, molars f. In other respects the teeth 

 most resemble those of the Brontotheridae. From this family 

 Diplacodon differs widely in its dentition and the absence of 

 horns. 



Etymology. — SlwXoos, double; aK-q, a point; 65ovs, tooth; 

 because the upper premolars had two inner cones. 



Present determination. — This genus is certainly 

 valid so far as it applies to the type species. (See 

 p. 439.) 



Diplacodon elatus Marsh, 1875 



Cf. Diplacodon elatus Marsh, this monograph, page 439 



Original reference. — Notice of new Tertiary mam- 

 mals: Am. Jour. Sci., 3d ser., vol. 9, p. 246, March, 

 1875; dated "February 20, 1875" (Marsh, 1875.1). 



Type locality and geologic horizon. — "Upper Eocene 

 beds of Utah"; horizon probably Diplacodon-Proti- 

 tanotherium-Epihippus zone (Uinta C, true Uinta for- 

 mation). 



Holotype. — A palate with dentition nearly complete, 

 parts of the skull and skeleton (Yale Mus. No. 11180). 



Generic characters. — The generic characters mingled 

 with the specific characters are given below. (See 

 also p. 382.) 



Etymology. — jSpaxvs, short; didaTrnxa, an interval; 

 dr]piov, beast; in allusion to the short diastema 

 between the lower canines and first premolars. 



Present determination. — The type of this genus is an 

 animal closely similar in size and in stage of evolution 

 to the Protitanotherium superhum of the upper Eocene 

 of Utah but differs in certain characters, which are 

 probably of generic value. (See p. 382.) 



Brachydiastematherium transilvanicum Bockh and Maty, 1876 



Cf. Brachydiastematherium transilvanicum Bockh and Maty, 

 this monograph, pages 382, 941 



Original reference. — -Mittheilungen aus Jahrb. K. k. 

 geol. Anstalt, Band 4, pp. 125-150, pis. 17, 18, 1876 

 (1876.1). Cf. Toula, Akad. Wiss. Wien Sitzungsber. , 

 Band 101, pp. 612 et seq., 1892 (1892.1). 



Type locality. — Andrashaza (Siebenbtirgen), Hun- 

 gary (Transylvania, eastern Hungary, about 150 miles 

 northeast of Belgrade). Collected in 1871 by Dr. 

 Alex. Pavay. 



