scott: toxodonta OF THE SANTA CRUZ beds. 
133 
is deceptive as to its actual capacity. The sagittal crest is thin and 
sharp and is often divided by a deep, narrow groove into two closely 
approximated parallel ridges. Though much longer proportionately than 
in Toxodon , the crest is yet quite short and divides anteriorly into the 
supraciliary ridges, which die away upon the forehead without reaching 
the orbital border. 
The orbit has a more inferior, as well as a more anterior, position than 
in Toxodon , the roof not forming a protuberance above the level of the 
forehead. The facial region is short, but very deep dorso-ventrally, 
especially when the mandible is in position ; in fact, the whole skull 
is curiously short, deep and massive in proportion to the size of the 
animal. The anterior nares are rather small and terminal in position, 
presenting almost directly forward, though with a slight inclination up- 
ward and backward, one of the most marked differences from the skull of 
Toxodon. 
The posterior surface of the skull, which can hardly, with propriety, be 
called the occiput, as it is so largely made up of elements which are not 
occipital, is low, very broad and almost D-shaped, with lateral and supe- 
rior borders describing a continuous and nearly semicircular curve. The 
occiput proper is of quite a different shape ; it is very broad at the base, 
forming here nearly the whole width of the posterior surface of the skull, 
but above the foramen magnum it is sharply constricted, expanding 
again, though but moderately, to the summit of the inion. The large 
area on each side which is thus left open, is filled by the element which 
Roth calls (’03) the pars mastoidea of the petrosal, but for reasons which 
will be explained in a subsequent section, is here regarded as being more 
probably the post-tympanic portion of the squamosal ; the relations of the 
parts are apparently much as in the pig. 
The upper view of the skull (PI. XIV) is very peculiar. From this 
point of view the outline is that of a somewhat irregular, truncated tri- 
angle, with the occiput forming the base, though the greatest width is 
over the zygomatic arches. The downward and backward slope of the 
occipital surface makes much of that surface visible and even the sessile 
condyles are prominently conspicuous. A highly characteristic feature is 
the great prominence of the auditory meatus and post-tympanic process at 
the supero-external angles of the occiput, and the elevated position of the 
zygomatic arches where their dorsal borders pass into the lambdoidal crest. 
