490 GEOLOGICAL SURVEY OF THE TEERITORIES, 



Professor Marsh described* a species allied to or identical with this 

 one, under the name of Brontotheriiwi ingens. It was based on a cranium 

 which has so great a resemblance to those of 8. trigonoceras that I have 

 regarded it as pertaining to it,t and written Professor Marsh's name as 

 a synonym, as it was published several months later than mine. Subse- 

 queutlyit Professor Marsh pointed out a number of characters which he 

 finds in my description as justifying him in retaining the species as dis- 

 tinct. He states that it is " nearly or quite twice as large in bulk. The 

 horn-cores also are very differently placed ; the nasals are more elon- 

 gated, and not emarginate at their extremities: the premaxillaries are 

 not prominent. The squamosals are greatly expanded, and there is no 

 postorbital process." Commencing at the last of these definitions, I 

 would remark that (1) the postorbital process is a rudiment in one of the 

 crania, and is entirely wanting in a larger one ; (2) the squamosal proc- 

 esses of the zygomata are not more expanded than might be looked for in 

 the adult male of S. trigonoceras, and would not be regarded as remark- 

 able iu this respect by one who has seen the larger expansions of the S. 

 1)11600 ; (3) thereisno difference iu the premaxillaries, which aremore prom- 

 inent than such species as 8. altirostris ; (4) " The nasals are more elon- 

 gate and not emarginate at their extremities;" Professor Marsh's figure 

 represents the nasals quite elongate as compared with other species, 

 and exactly as in some of my specimens ; the emargination is slight and 

 is not always present in 8. trigonoceras ; (5) there is no difference in 

 the form and position of the horn-cores ; (G) the superior size : I have 

 no crania so large as that described by Professor Marsh, which he states 

 to be 0™ .915 long and 0"^ .558 wide through the zygomas, with horn-cores 

 20 inches apart at the apices. My largest measures 0°^ .762, 0" .432, and 17 

 inches, respectively. The specimen from which vertebrae and a premolar 

 tooth were described above approaches nearer in dimensions; thus, the 

 fourth premolar measures — 



S. trigonoceras. S. ingens. 



Leugthof crown 0.050 0.053 



Width of cro*vn 065 .069 



While still under the impression that the species are the same, I defer 

 final conclusion until all of my material is in suitable condition for study 



Symboeodon ophryas. Cope; Miohasileus ophryas, Cope, Pal. Bull., 

 1^0. 15, 3 ; Proc, Amer. Assoc. Adv. Sci., 1873, 108. 

 Established on a cranium with nearly complete dentition, but without 

 mandibular ramus. Head elongate, concave in profile from the iuteror- 

 bital region to the supraoccipital crest. This is transverse and concave, 

 the posterior borders of the temj)oral fossae extending behind it. These 

 fossae leave a narrow, flat vertex between them. Zygomatic arch stout 

 and rather deep ; a strong postglenoid process. Nasal bones very mas- 

 sive; their free portion elongate, hornless. A massive horn-core rising 

 from above each orbit; no superciliary angle or ridge. Orbit not in- 

 closed behind. Of molar teeth only P. m. 3-4, M. 1-2-3, preserved ; the 

 M. with two, the P. m. with one inner cone and two outer continuous cres- 

 cents. The latter send inwards to one side of the cones a transverse 

 ridge. Incisors and canines unknown. The malar bone is flat and i>ro- 

 portionally deep below the orbit. Front concave transversely just be- 

 hind between the horns. Latter massive and a little compressed. Nasal 

 bones convex longitudinally and transversely, slightly rugose. Trans- 



*Amer. Journ. Sci. Arts, 1874, Jan., p. 85. 



t Bulletin of U. S. Geological Survey of Terrs., No. 2, p. 28. 



i American Naturalist, Feb., 1874, p. 84. 



