MEGACEROPS TYLERI 



447 



GENERAL DESCRIPTION 



The skull (Plate III, Figs. 1-4). — The skull was partially exposed 

 as it lay in the quarry, so that the occiput and the left zygomatic arch 

 have been destroyed by weathering. The remainder is in admirable 

 preservation, except for the distortion noted above. In spite of the 

 fact that the union of the epyphises with the vertebral centra is as 

 yet imperfect, which, as Marsh has shown, occurs rather late in the 

 titanotheres as in the elephants, the sutures are almost obliterated 

 from the skull, as one can only distinguish the squamoso-jugal suture 



Fig. 1. — Basal section of the horns of Megacerops tyleri taken in a plane 

 perpendicular to their axes. One-quarter natural size. 



of the zygomata, and that on the inferior side of the nasals. The 

 general contour of the horns is well shown in Plate III, Fig. 3, and in 

 the sections here shown, though allowance must be made for the crush- 

 ing backward of the right and the crushing forward of the left horn. 

 Toward the summit the horns become rounder in section, and they 

 • terminate in a much-roughened area, which is somewhat flattened, 

 and which Osborn describes as "incompletely 

 ossified." Another roughening of a similar 

 character, though not so pronounced, marks 

 the summit of each hornlet, and there is an 

 entire absence of any vascular impressions over 

 the surface of the horn, as in the horn cores of 

 the hollow-horned artiodactyls and the Cera- 

 topsia among dinosaurs. This leads the author 

 seriously to doubt the accuracy of those restor- 

 ations of the animal wherein these prominences 

 are represented as sheathed with horn. On the 

 contrary, it would seem, from the similarity of 

 the roughened patches to those on the rhinoceros 

 nasals, as though the entire prominence had been clothed with skin 



Fig. 2. — Vertical 

 section through the zygo- 

 matic arch at the point 

 of its greatest expansion. 

 One-quarter naturalsize. 



