DISCOVERY OF THE TITANOTHERES AND ORIGINAL DESCRIPTIONS 



227 



the name syceras is derived, in reference to the approxi- 

 mation of the horns at their bases. Portion of right 

 frontal, coossified nasals, and right horn. (See fig. 

 186.) 



Characters of type. — Cope writes: 



It differs from the two species of that group now known, 

 the M. proutii Leidy and the M. Hchoceras S. and 0., in the 

 very close approximation of the basis of the horns and the pres- 

 ence of a strong angle or ridge connecting them, so that the nasal 

 bones are in a different plane from that of the front. The 

 entire width of the skull at the basis of the horns is not greater 

 than the length of each horn above the nasal notch. The 

 horns are not long, and the section of their base is a longitudinal 

 oval, flattened on the external side. Summit subround. The 

 nasal bones are fiat, with broadly rounded extremitj', and are 

 much wider than long. 



The width of the nasals at the base of the horns is 116 milli- 

 meters; length of do. from do., 70; diameters of bases of horns; 

 anteroposterior, 94; transverse, 67; length of horn from nasal 

 notch, 160; width of muzzle at bases of horns inclusive, 160. 



Etymology. — aiiv, together; /cepas, horn; because the 

 horns were set very near to each other at the base. 



Present determination. — M. syceras is at present 

 indeterminate or possibly a synonym of M. angustigenis, 

 both are provisionally referred to the genus Megacerops. 



LAST FIVE SPECIES DESCRIBED BY MARSH, 1890-91 

 Diploclonus Marsh, 1890 



Cf. Diploclonus, this monograph, page 499 



Original reference. — Am. Jour. Sci., 3d ser., vol. 39, 

 p. 523, June, 1890 (Marsh, 1890.1). 



Type species. — Diploclonus amplus. (See below.) 

 Characters. — Marsh writes: 



One of the most marked features is seen in the horn cores, 

 which are high, compressed transversely, and have a prominent 

 knob on the inner superior margin about one-third of the dis- 

 tance to the summit. Seen from the front the horn cores thus 

 appear to be branched. It is probable that in life this feature 

 was still more evident, and the covering of the horn core may 

 have shown an actual division, but this can not be determined 

 from the present specimen. There is a sharp ridge at the base 

 of the horn cores on the outside. The nasals project but very 

 little in front of the horn cores. The zygomatic arches are 

 especially strong and widely expanded. The posterior nares 

 have their front margin opposite the back of the last upper 

 molars. 



There were apparently but two upper incisors — that is, one on 

 each side — and no diastema exists behind the canines. The 

 premolars have a strong inner basal ridge, and the last upper 

 molar has two inner cones. This genus appears to be most 

 nearly related to T'iianops, but the horn cores will distinguish 

 it readily from all known forms of the Brontotheridae. 



Etymology. — 5t7rX6os, double; kXwv, a twig; in allusion 

 to the branched appearance of the "horn core." 



Present determination. — The genus is now regarded 

 as valid by Osborn. 



Diploclonus amplus Marsh, 1890 



Cf. Brontops amplus, this monograph, page 504 



Original reference. — Am. Jour. Sci., 3d ser., vol. 39, 

 p. 523, June, 1890 (Marsh, 1890.1). 



Type locality and geologic horizon. — South Dakota; 

 " Brontotherium beds" (= Chadron formation, or Titan- 

 otherium zone). 



Type. — "Nearly complete skull, in good preserva- 

 tion, but without the lower jaws." Yale Mus. 12015a. 

 (See fig. 187.) 



Specific characters. — Marsh writes: 



The skull measures 28 inches from the front of the nasals to 

 the back of the occipital condyles and 24 inches in greatest 

 width across the zygomatic arches. The space occupied by the 

 upper dental series is 13J^ inches, and by the true molars 8 

 inches. 



Etymology. — amplus, broad, in allusion to the great 

 breadth of the skull. 



FiGUEE 187. — Type skull of Diploclonus amplus 

 After Marsh. One-eighth natural size. A', Side view; A', front view 



Present determination. — This species is cither an 

 aberrant stage in the evolution of Brontops — that is, 

 a sport — or a lateral phylum of Brontops. 



Teleodus Marsh, 1890 



Cf. Teleodus, this monograph, page 481 



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

 39, p 524, June, 1890 (Marsh, 1890.1). 



Type species. — Teleodus avus Marsh. (See below.) 

 Generic characters. — Marsh writes: 



The present genus is allied to Brontotherium but differs from 

 it in having six lower incisors instead of four. It has the same 

 number of inferior premolars and molars, and these teeth are 

 similar in the two genera. From Diplacodon of the upper 



