T^NIODONTA. 
159 
available for present determination. The superior are all remarkable for 
the great exposure of their external faces as compared with their internal, 
and the extension of the enamel on the outer face of the very thick external 
root, which is not distinguished from the crown. The premolars have two 
of the roots connate, forming a support to the greater part of the crown. 
The worn surface is in form something like the Greek a?, the deep emargi- 
nation being internal. The inferior molars have greater antero-posterior 
than transverse diameters. The enamel is more extended on one side than 
the other, covering the exposed portions of the roots. The grinding-surface 
is plane, and has the form of a horizontal 02 ; the limbs being angulate, as 
in the Greek N. The enamel of the oblique molars is quite thin. A portion 
of a large molar which I originally described as having three roots is of 
uncertain position, owing to a portion having been lost. Two sides of the 
crown stand on a single root of crescentic section which is abnormally 
divided by a fracture. There were tliree prominent tubercles on the cir¬ 
cumference of the crown, but injuries it has sustained prevent the descrip¬ 
tion of its true form. 
This genus apparently occupies a position between the single-rooted 
and many-rooted genera of the group. It differs from AncMppodus and 
its immediate allies in the greater simplicity of the form of the inferior 
molars, which are composed in the latter of two V’s, somewhat as in many 
Insectivora. 
Ectoganus novomehicanus, Cope. 
Plate xl, fig8. 34-39. 
Calamodon novomehicanus^ Cope, Eeport Vert. Foss. New Mexico, U. S. Geog. Survs. 
W. of 100th M., 1874, p. 65 Id., Ann. Report U. S. Geog. Survs. W. of 100th 
M., 1874, p. 118. 
This species is represented by a superior and perhaps an inferior 
incisor tooth. The former obviously belongs to a species of JEdoganus, but 
exhibits strong characteristic distinctions from the corresponding tooth of 
the JE. gliriformis. It belongs to an individual of larger proportions than 
the type-specimen of the latter. 
The superior incisor has the usual compressed form, and is concave on 
one side and convex on the other. The two enamel-covered edges are thick, 
and converge gently. The enamel bands themselves are extended chiefly 
