W. K. GREGORY — TUPAIHXfi AND EOCENE LEMURS 



the alveoli for the second and third incisors, for the canine, premolar! 

 and premolar,, are well preserved ; the incisors were gently procumbent ; 

 the canine was small, single-fanged. erect, and located well back on the 

 side of the jaw: p x . p 2 were small, very simple teeth: p 3J p 4 , and the 

 three molars, all perfectly preserved, much resemble those in Tupaia, 

 and differ markedly from those in Ga'Urix. Lepticids, and other Eocene 

 Insectivores. 



Entomolestes is considerably more primitive than either Tupaia or 

 Ptilocercus in the following characters : First, in its very minute size. 

 the jaw being no bigger than that of a shrew: secondly, the jaw retains 

 the complete Eutherian dentition, the formula being 3.1.4.3. whereas 



the modern Tupaiids have lost p — : third, the tendency toward dipro- 



todonty and reduction of the canine, so prominent in P tiocercus, is here 

 only suggested : fourth, the symphysial region is shallower and the ramus 

 more curved below — characters seen in Jurassic Insectivores : fifth, the 

 molars had lower crowns than in Tupaia; sixth, the cingulum at the 

 anteroexternal base of the trigonid. vestiges of which are retained in 

 Ptilocercus, was pronounced: seventh, the teeth were in continuous series 

 as in Ptilocercus. whereas in Tupaia the canine and anterior premolars 

 have become irregularly spaced. The sole point in which the Entomo- 

 lestes jaw appears to be aberrant is in the slightly reduced size of m 3 . 

 Thus Entomolestes carries the Tupaiida? back to a primitive Middle 

 rne type, the teeth of which, as Dr. Matthew* noted, were partly 

 transitional to the type shown in Apatemyida?. Mixodeetida?. and primi- 

 tive Lemuroidea. But from all of these it is distinguished by retaining 

 the complete Eutherian dental formula and by having the talonids of the 

 lower molars not expanded : it is also without a hypoeonulid on m 3 . 



HAECTus ax Eocene Lemur 



In the same formation, the Bridger. along with this very primitive 

 Tupaiid the American Museum Expeditions found several incomplete 

 skeletons of one of the most primitive known Primates,, the genus 

 tharetus. This material is of signal importance in the problem of Pri- 

 mate genealogy, and it has been generously placed in my hands for de- 

 scription by Doctor Matthew. 



If the postcranial skeleton of Xotharctvs had been well known in 

 Cope's time, without admixture of foreign material, much confusion 

 would have been saved. If the limbs and vertebra? had been known 



•Op. cit.. p. 53' 



