446 Bulletin American Museum of Natural History. [Vol. XXXIV, 
I can find no basis for family separation from J arsius of this group of 
Eocene lemuroids. Wortman! separates the modern genus “ because of the 
modification of its hind limbs and other modernized characters.” But I 
cannot find that he had any evidence in regard to the construction of the 
hind limbs in any of the Eocene genera, and our material shows that in at 
least one of them, probably Hemiacodon, the hind limbs were very like those 
of Tarsius, although less specialized. The same is true of Necrolemur,? which 
Wortman places in the Anaptomorphide. There are several characters 
in addition to the larger braincase in which the skull of Tarsius is more 
modernized than that of the Lower Eocene “ Anaptomorphus.” But in 
some other genera of this group the dentition is much nearer to Tarsius, 
and the skull construction may likewise have been nearer. In any case, 
the differences which can be cited are not as wide or fundamental as those 
between Tertiary and modern genera which no one thinks of separating 
into distinct families.2 The affinities of the group and the relationships 
of Necrolemur and other European genera will be more fully discussed by 
Dr. Gregory. xs 
Interrelationship of the Eocene genera. So far as the dentition indicates, 
these genera fall into four groups. The first including Omomys and Hemiaco- 
don is characterized by slender jaw, semi-procumbent front teeth, i; and c, 
somewhat enlarged, lower premolars not crowded, ps triangular at base, 
lower molars with small trigonid, paraconid median, last molar unreduced. 
In the second, including Washakius and Shoshonius, the jaw is short and 
moderately deep, the front teeth nearly vertical, both incisors small, canine 
of moderate size, lower premolars somewhat. crowded, ps with quadrate base, 
lower molars with an extra cusp (metastylid) on the postero-external angle 
of the trigonid, paraconid median on me-3, last molar unreduced. In the 
third group including Uintanius alone, the jaw is short and deep, front 
teeth not fully known but apparently small and more or less vertical, 
premolars crowded and ps;-, enlarged blade-like, molars with low crowns, 
median paraconid, last molar unreduced. The trigonids of the molars 
are peculiar in having the metaconids set further back than the protoconids 
instead of nearly opposite. The fourth group includes T'etonius and Absa- 
rokvus and is distinguished by short deep jaw; one or two front teeth enlarged, 
more or less vertical; premolars crowded, p3-4 enlarged, turgid; molars 
exceptionally short and wide with paraconids internal and connate with 
metaconids, last molar much reduced. The enlarged premolars in this 
1 Wortman, 1904, Amer. Jour. Sci., Vol. XVII, p. 28. 
2 Schlosser, 1907, Neues Jahrb., Festb., s. 197-226, taf. x. 
3 Compare for instance the range of diversity in dentition among modern Mustelide, 
or the differences between Oligocene and modern Canide. 
