Marsh Collection, Peabody Museum. 29 



Family Anaptomorphidai. 



The family is divisible into two subfamilies, as follows : 



Nine teeth in the lower jaw. Omomyinae. 



Eight teeth in the lower jaw. Anaptomorphinae. 



Subfamily Omomyinw. 



The genera of this subfamily are distinguished by the fol- 

 lowing characters : 



Lower molars having three cusps on trigon, the anterior cusp 

 of the last molar not being as distinct as that of the others ; heel 

 of last molar with three cusps ; first and second molars narrow in 

 front, with wider heel ; last molar slightly smaller than first and 

 second, with heel very little wider than trigon ; fourth lower pre- 

 molar with small internal cusp and an indistinct heel ; third lower 

 premolar without internal cusp or heel, but having a pointed 

 crown whose summit rises above the crowns of the other teeth ; 

 canine larger than incisors or second premolar ; neither first nor 

 second incisor enlarged ; superior molars tritubercular, with 

 rounded external angles, and but moderately extended trans- 

 versely ; intermediates faint or absent ; a rudimental postero- 

 internal cusp present on first, less distinct on second, and absent 

 on third molar ; first and second molars subequal, third slightly 

 smaller. Omomys. 



Lower molars having three cusps on trigon, the anterior of the 

 third being least distinct ; heel of last molar with three cusps ; 

 first and second molars narrow in front, with broader heel ; last 

 molar longer but narrower than first and second, with heel very 

 little wider than trigon ; fourth inferior premolar with strong 

 internal cusp and distinct heel ; third premolar with rudimental 

 internal cusp and heel; summit of crown not high and pointed as 

 in Omomys / second premolar, canine, and external incisor small 

 and of equal size ; first incisor enlarged ; superior molars trituber- 

 cular, with squarish outline externally, and with intermediates 

 very distinct; a small distinct postero-internal cusp on first and 

 second molars, but absent on third ; a strong cingulum continued 

 around inside of crown, and developing an additional cusp at the 

 antero-external angle of the crown. Hemiacodon. 



Lower molars having three cusps on trigon, the anterior cusp 

 of the last molar being absent ; heel of last molar without distinct 

 internal cusp ; first and second molars without much disparity in 

 width between trigon and heel ; last molar narrow and reduced ; 

 premolars, incisors, and canines unknown ; superior molars tritu- 

 bercular, with rounded external angles ; intermediates small, but 

 distinct ; a postero-internal cusp on crown of second molar; cingu- 

 lum continued around in front, developing a small cusp internal 

 to the main internal cusp ; last molar considerably reduced. 



Euryacodon. 



