Char, specif. — The front of the crown is divided longitudinally 

 by a prominent median keel and the borders are not serrate. The 

 keel is only moderately prominent at the lower part of the crown. 

 The back of the crown is divided into three faces by two straight 

 longitudinal parallel solid angles, and the crown is contracted near 

 the base by the lateral bevels for the adjacent growing teeth, All 

 these faces are covered by cementum, whose roughness is granulai 

 in character. The external surface of the jaw-bone has precisely 

 the same character, so that the apices of the teeth only appear as 

 prominences of its border. 



The typical specimen is that of an individual of moderate dimen- 

 sions; measurements of a tooth of a gigantic individual are given 

 below. 



Measurements. m. 



Length of a series of five teetli 023 



Protrusion of crown of largest tooth 006 



Diameter " " " 006 



Length of crown above lateral apical facets of larger animal .013 



Diameter of crown at same point f anteroposterior -OH 



transverse . . . .009 

 Width of median face of "back" 005 



Diclonius perangulatus, sp. nov. 



This abundant species of herbivorous dinosaur has left its shed 

 teeth in many localities of the Fort Union horizon, in company 

 with those of the Trachodon mirabilis, Palseoscincus costatus, 

 and other large reptiles. Teeth with complete apices are rare. 

 The marked character of the species is seen in the prominence of 

 the median angular ridge which divides equally the cutting face 

 of the crown from apex to base. The prominence increases down- 

 wards so that the transverse diameter becomes greater than the 

 antero-posterior, in some cases being diamond-shaped in the trans- 

 verse direction. Its position is symmetrical, or nearly so. The 

 lateral borders are smooth, one specimen displaying a faint trace 

 of crenation near the apex. There is no shank or root in any of 

 the teeth preserved, and the basis is excavated on the side away 

 from the cutting edge for the apex of the succession al tooth. A 

 band of roughened cementum extends round the base, and is con- 

 tinued upwards on each side opposite the cutting face. This side 

 presents three faces, a narrow median, and two wider lateral. The 

 latter are slightly concave, and are probably adapted to the apices 



