CREODONTA. 
123 
DIDYMIOTIS, Cope. 
System. Cat. Vert. Eocene ITew Mexico, U. S. Geog. Survs. W. of lOOtli M., 1875, p. 11. 
Inferior molars six, consisting of four premolars and two true molars. 
True molars, a posterior tubercular and anterior tubercular sectorial, i. e., 
with, three elevated cusps and a posterior heel. Premolars with a lobe 
behind the principal cusp. The canine'teeth are directed forward, and are 
very close together, so that it is doubtful whether there were any incisors. 
An ungual phalange of the typical species is strongly compressed. 
The humerus in this genus is distally expanded transversely, and the 
margin is pierced by the humeral artery. The astragalus exhibits two 
entire trochlear faces; the wider external and directed intero-superiorly, 
the inner presenting supero-interiorly. They are separated by an obtuse 
longitudinal angle, and are little or not at all concave transversely. The 
form is depressed. The head supports a single transverse convex facet for 
the navicular, and, with the neck, is as long as the trochlear portion. 
' The resemblance of this genus to the existing Viverra^ in the dentition 
of the lower jaw, is so great that the only distinctive feature apjoears to be 
the deficiency of the full number of incisors. 
Didymictis protenus, Cope. 
Plate xxxix, figs. 1-9. 
Didymictis protenus, Cope, System. Cat. Vert. Eocene New Mexico, U. S. Geog. Survs. 
W. of 100th M., 1875, p. 11. 
Limnocyon protenus, (]ope. Report Vert. Foss. New Mexico, G. S. Geog. Survs. W. of 
100th M., 1874, 15; Id. Ann. Report U. S. Geog. Survs. W. of 100th M., 
1874, p. 126. 
This fine species left its remains in moderate abundance in the Wasatch 
beds of the Gallinas country. As usual, the lower jaws were most com¬ 
monly obtained, and these represent six individuals. The size of this bone 
is that of the largest varieties of the Eed Fox. 
Selecting as typical of the species the most completely preserved 
specimen, it may be observed that the ramus is slender and produced 
anteriorly. 'The symphysis is narrow, the suture being close to the base of 
the crown of the canine where it issues from the alveolus. The posterior 
extremity of the suture is opposite to the anterior border of the third pre- 
