188 NEBRASKA GEOLOGICAL SURVEY 



feet (915 mm.) apart at the tips, and curve downward slightly. 

 Each tusk is 4 feet (1,220 mm.) long. One foot of the tusk is 

 firmly imbedded in the jaw, and an additional 6 inches is partly 

 sheathed and buttressed by the maxillae. Since the tusks are 

 sheathed by the maxillae in the typical Proboscidea, they have been 

 considered by some as morphologically canine teeth. The skulls 

 of young elephants show that the tusks are erupted from the pre- 

 maxillae and are incisors. 



Incident to grow r th from persistent pulps, the young incisors 

 naturally outgrow the limits of the premaxillae, and invade the 

 maxillae. They are incisors grown indefinitely large. In most 

 Tetrabelodons, there is a conspicuous bifurcation of the maxillary 

 sheath, but especially so in Eubelodon morrilli. Beyond the tips 

 of the maxillae, the tusks project 30^/2 inches (776 mm.). 



The skull is still in the hands of preparators, and has not yet 

 been fully worked out or turned over, to show the anterior narial 

 apertures. From observation in the quarry, it seems that the 

 surface for the attachment of the muscles of the proboscis is 

 restricted in area. Undoubtedly the proboscis, that most distinc- 

 tive badge of the group, was only partly developed, and was short. 



The posterior narial aperture is large, nearly circular, and 

 with vertical walls. Its antero-posterior diameter is 4^/2 inches 

 (115 mm.). The transverse diameter is 3^2 inches (90 mm.). 

 From its anterior border to the tips of the maxillae is 24 inches 

 (610 mm.). The basicranial elements, and the palate lie in a 

 plane perforated by the postnarial aperture, while in Elephas 

 these same parts are at right angles. 



That the cancellous portions of the bone of the brain box lack 

 the extreme inflation of air cells common in Elephas is quite 

 apparent, and is readily accounted for. Though the head was very 

 large, larger than an ordinary elephant, the tusks and trunk were 

 not ponderous, and did not demand such an abnormal surface area 

 for the attachment of muscles. 



The pelvis, including sacrum and sacral spine, is perfectly 

 preserved, and indicates an animal of large size. The acetabulum 

 measures 6 l / 2 inches (165 mm.) in diameter. The neural arch 

 measures i l /> inches (38 mm.) The pelvic aperture is 16 inches 



