This family includes certain fossil forms of Lower Eocene age from the
phosphatic deposits of Quercy in France, the {115}Wasatch strata of
Wyoming, and the Puerco beds in New Mexico. Their dental formula is the
same as that of existing Lemurs, namely I2/(2-1), C1/(1-0), P(2-3)/(2-3),
M3/3. In some of the genera there is a tendency to develop, as Cope has
pointed out, large cutting teeth in the position of incisors, "thus
approaching the Aye-Aye." The posterior pre-molars are more simple than the
anterior true molar, a character which indicates some relationship to the
Mouse-Lemurs (_Chirogale_). The mastoidal or posterior portion of the
ear-capsules, and the neighbouring squamosal region of the cranium are
swollen, as among the Galagos.