280 THE OSTEOLOGY OF ELOTHEEITJM. 



chamber, but toward the ventral side they rapidly contract, forming narrow strips 

 between the squamosal and frontal. Throughout their length the parietals unite to form 

 the very high, thin and plate-like sagittal crest, which is one of the most characteristic 

 features of the skull. In the Euroj^ean species, E. magnum, this crest has a remarkably 

 straight and horizontal course, but in the known American species it is gently arched 

 from before backward. Large sinuses are develojDed in the parietals, so that the cerebral 

 chamber is even smaller than it appears to be, when viewed from the outer side. These 

 sinuses extend over the entire roof of the cerebral fossa, even invading the supraoecipital ; 

 they appear to be traversed by numerous small trabecule, the ends of which are seen, in 

 the sagittal section, embedded in the matrix which fills the sinuses. 



The front ah are much larger than the parietals. In the postorbital region they are 

 very narrow, in conformity with the very small size of the brain, but at the orbits they 

 expand widely to form the broad, lozenge-shaped forehead, which is convex from side to 

 side, though slightly depressed, or " dished " in the middle ; the supraciliary ridges are 

 very inconspicuous. Anteriorly the frontals diverge to receive the nasals between them, 

 sending forward long, pointed nasal processes, which, owing to the great elongation of the 

 muzzle, are widely separated from the premaxillaries. The orbit is large and projects 

 prominently outward; it is completely encircled by bone, the long and massive postorbital 

 process of the frontal uniting suturally with the shorter process of the jugal. The orbits 

 do not rise above the level of the forehead, as they do in Hippopotamus, and present 

 more anteriorly, less directly outward, than in that animal. Mention has already been 

 made of a groove on the orbitosphenoid, which terminates below and behind in the fora- 

 men lacerum anterius ; this groove is continued upward and forward upon the frontal, 

 steadily widening as it advances. The postero-superior ridge bounding the groove is the 

 more prominent : it extends almost to the postorbital process, from which it is separated 

 by a distinct notch, while the anteroinferior ridge dies away within the orbit. In most 

 of the American species the forehead rises very gradually and gently behind to the sag- 

 ittal crest, but in K. ingens the rise i- much more sudden and steep. The frontal sinuses 

 are large, giving the convex shape to the forehead which has been described; these 

 sinuses appear to communicate with those formed in the parietals. 



Except posteriorly, the squamosal forms but little of the side-wall of the cranium, its 

 suture with the parietal curving abruptly downward and forward; its compressed and 

 prominent hinder margin forms nearly the whole of the lambdoidal crest, though a con- 

 tinuation of it extends upward upon the supraoecipital, ending in the wing-like processes 

 ot that hone. The zygomatic process is enormously developed; it extends widely out- 

 ward from the side of the skull as a massive, vertical plate, which is shaped much as in 

 Hippopotamus, and i> not continued forward as a broad, horizontal shelf, such as is found 



