Diclonius perangulatus, Cope, 1876

Cope, E. D., 1876, Descriptions of some vertebrate remains from the Fort Union beds of Montana, Proceedings of the Academy of Natural Sciences of Philadelphia 28, pp. 248-261 : 254-255

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 , Palaeoscincus costatus , and other large reptiles. Teeth with complete apices are rare. The marked clharacter of the species is seen in the prominence of the medlian angular ridge which divides equally the cutting face of the crown from apex to base. The prominence increases downwards so that the transverse diameter becomes greater than the antero-posterior, in some cases being diamond-shaped in the transverse 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 cuttinlg edge for the apex of the successioinal tooth. A band of roughened cementum extends round the base, and is continued upwards on each side opposite the cutting face. This side presents three faces, a narrow mediain, and two wider lateral. The latter are slightly concave, and are probably adapted to the apices of the successional teeth; the former is often slightly concave, and is the seat of most rapid attrition. The lateral facets disappear at a distance below the apex, where the non-cutting side is strongly convex, and covered with a coarsely rugose cementum; the rugosity including pits.

Measurements.	M.
Length of a shed tooth	.011
antero-posterior Diameter of crown transverse	.010.012
Width of facet for successional crown	.006
Width of posterior facet	.005
Width of cutting face of another near apex	.008
Antero-posterior diameter of do. at do.	.010

The prominence of the median angle with othier points distinguishes this species from the Cionodon arctatus . The size is larger than that of the known specimens of that species, equalling that of the largest of the order. (See Report of U. S. Geological Surv. Terrs. II., 4to, for description of genus Cionodon.)

Specimens of this species have been referred by Dr. Leidy to his Trachodon mirabilis .