108 



the base, and, internally, appears to liave been lost from the corresponding 

 position l)y erosion. Externally, it is longitudinally rugose, and the rugosity 

 appears to be greater toward tlie point, and, to some extent, is divergent 

 toward the trenchant borders. Internally, the rugosity of the enamel is less 

 marked, and toward the point it is worn off for several inches along the axis 

 and near the borders from the attrition of an opposing lower tooth. The ex- 

 tent of attrition would apparently indicate large lower canines. 



At the broken base of the specimen the borders of the exposed pulp cavity 

 are nearly 4 lines thick. The fore and aft diameter of the tooth 2 inches 

 below the broken base is a little under 2 inches ; the thickness is 13 lines. 

 The breadth of the tooth just Ijefore expanding in the lance-head extremity 

 is 1^ inches. The widest part of the latter appears to have been a couple of 

 lines greater. 



The tusk above described, though apparently according in form with those 

 of Dinoceras mirabiUs, as described by Professor Marsh, exhibits different 

 proportions, having less breadth and greater thickness. Thus Professor 

 Marsh gives as the diameters of the tusks of D. mirahilis 64 millimeters 

 breadth, and 25 millimeters thickness. The tusk above described has a 

 breadth of 50 miUimeters, and a thickness of 28 millimeters. 



From the description of the skull of Dinoceras given by Professor Marsh, 

 as before intimated, I have been led to view the large tusks above described, 

 and originally referred to a carnivore with the name of Uintamastix, as really 

 pertaining to Uintatherium, and perhaps to the same species as that indicated 

 by the cranial specimen referred to TJ. rohustum. 



The molar tooth of Uintatherium, represented in Figs. 13, 14, found with 

 the large tusk, has the same form and constitution as the upper molars first 

 referred to the genus, except that it is considerably smaller, and has no 

 tubercle behind the summit of the conjunction of the lobes of the crown. 

 Proportionately, also, the basal ridge is much better developed at the inner 

 part of the crown, where it is continuous with the stronger ridge in front and 

 behind. The antero-posterior diameter of this tooth is 11^ lines, and its 

 transverse diameter is estimated at 13J lines. 



The tooth I supposed to be an upper premolar of U. rohustum; if, how- 

 ever, it is a true molar, its comparatively small size, and the absence of the 

 characteristic tubercle on the posterior slope of the conjunction of the lobes 

 of the crown, as existing in the species just named, would indicate that it 



