Dysganus haydenianus, Cope ED, 1876

Cope ED, 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 : 251

Dysganus haydenianus , nov. sp.

Represented by a number of teeth found in such relation that they are supposed to belong to two individuals.

They differ materially in form from those of the D. encaustus , and exceed any of them in size.

The base of the tooth possesses the thick investment of rough cementum, and has a slope away from the base of the crown. The form of the crown is peculiar in possessing a lateral face placed at a strong angle to the usual face, and separated from it by a strong protuberant angular ridge. This angular cuttinig face would resemble that of the Diclonii were it not that the body of dentine of which it is composed is a flat plate inistead of a triangular segment of a subquadrate prism. Each face has a separate plate, which is separated from the other by a suture. A solid mass fills the angle between them, which is divided by a groove produced by the pressure of the angle of the face of the succeeding tooth which fits it. The wider of the " front " faces is divided by a low longitudinal ridge. Both of the faces are bounded by an external incurved ridge which cause them to have a concave surface.

A tooth of a size equal to that of the one just described was found with it, has a form more nearly like that of D. encaustus , in the less degree of prominenice of the lateral angle. It displays but a single posterior cementum-like mass, which presents considerable lateral faces as well as a posterior onie, as in the first described tootlh.

Dedicated to Doctor F. V. Haydenl, U. S. Geologist.