278 THE OSTEOLOGY OF ELOTHERITTM. 



II. The Skull. 



The skull of Elotherium is one of the most remarkable features of this very curious 

 animal. It is characterized by great length and slenderness, with the supraoccipital and 

 nasal bones lying in the same horizontal plane. The muzzle is exceedingly long and 

 narrow, and tapers somewhat anteriorly, though expanded by the sockets of the great 

 tusks ; the orbit has been shifted far back, its anterior border being, in some species, over 

 m ^, and in others above m K Tbe cranium is short and of absurdly small capacity, 

 which, with the great temporal openings, gives an almost reptilian appearance to tbe 

 skull when viewed from above or below. The sagittal crest is very high and thin, and 

 the zygomatic arches, though rather short, are enormously developed. One of the most 

 peculiar features of the skull is the great, compressed plate which is given off from the 

 ventral surface of the jugal and descends below the level of the lower jaw, and this gro- 

 tesque appearance is further increased by two pairs of knob-like processes on the ventral 

 borders of the mandible. The occiput (PI. XVIII, Figs. 1, 2) is high and very broad at 

 the base, but narrowing rapidly to the summit ; above the foramen magnum it forms a 

 broad, flat ]3rojection of almost uniform breadth, with a very deep fossa on each side of it. 



The basioccipital is stout and rather short, keeled in tbe median ventral line and 

 slightly contracted to receive the auditory bullae ; at its junction with the basisphenoid it 

 forms a pair of small, roughened tubercles. Tbe exoccipitals are very large bones, espe- 

 cially in the transverse direction along the base of the occiput, dorsally they narrow fast. 

 Above the foramen magnum they form the very broad, prominent and nearly square j)ro- 

 jection which has already been mentioned; this is thick and is filled with cancellous bone, 

 the fossa for the vermis of the cerebellum making but a slight depression upon its internal 

 face. On each side of the projection is a large and deep triangular fossa, which, how- 

 ever, is not confined to the exoccipital, the periotic and squamosal both being concerned in 

 its formation. The inferior part of the exoccipital extends widely outward, reaching to 

 the line of the glenoid cavity, and ending in the large, prominent and massive, but not 

 elongate paroccipital process. In this region the exoccipital is brought very close to the 

 zygoma, but, ventrally at least, does not quite touch it, a narrow band of the tympanic inter- 

 vening between them. The foramen magnum is strikingly small and of a transversely oval 

 shape. The occipital condyles are relatively rather small, especially in the vertical dimen- 

 sion, laterally they are well extended, and they are widely separated both above and below. 

 In the very large E. imperator the external angles of the condyles are abruptly truncated 

 in a curious way, and bear flat articular surfaces, though in some individuals this trunca- 

 tion is found only on one side : while in the smaller species the condyles are of the usual 

 form. The supraoccipital is a large bone, widest at the base (i. e., the suture with the 

 exoccipitals) and narrowing dorsally. Superiorly it is drawn out into two posterior wing- 



