684 The American Naturalist. [August, 
do not think that this explanation is probable, and for the 
reason that no primitive ancestor of the Primates would have 
had a closed orbit and proclivous lower incisors. At the time 
the Apes and Lemurs diverged from a common stock, this stem 
form would have had characters more like those of the Adapis, 
and not until very late, geologically speaking, were the pecu- 
liar incisors of the Lemurs developed. Primate with closed 
orbits do not appear until the Middle Miocene. We are then 
forced to the conclusion that one set of characters of Nesopithe- 
cus is due to convergence. As Nesopithecus has so many pecu- 
liar characters only found in the Anthropoids, including the 
structure of the true molars, I conclude with Major that Neso- 
pithecus is really an Anthropoid whose anterior dentition 
through convergence has come to resemble that of the Lemurs. 
Lastly I do hold that the discovery of Nesopithecus demonstrates 
that Apes and Lemurs are genetically related. 
The characters of the skeleton of Tarsius are nearly all those 
of the Lemurs; the extreme specialization of the pes of Tarsius 
* is clearly a lemurine character, and we can observe how this 
elongation of the tarsus is produced. In Lepidolemur the 
elongation of the caleaneum and navicular commences, the 
extension of these bones is carried still further in Cheirogaleus, 
and reaches its culmination in Tarsius. Of course this is not a 
phyletic series, and I merely mention it to show how the elon- 
gation of the tarsus in Tarsius is developed, and from a more 
normal condition found in the typical Lemurs. Tarsius differs 
from most of the Lemuroidea in not having the fourth digit of 
the manus longer than the others, the extension of this digit 
attains its greatest development in the most specialized group 
of the Lemurs, the Indrisinæ. The Indrisines are clearly the 
most highly differentiated division of the Lemurs; this is 
shown in their more highly developed brains, reduction in the 
length of the facial as compared to the cranial axis of the 
skull, the pseudo-selenoid superior molars, and lastly the great 
length of the posterior limbs in contrast with the anterior mem- 
bers. In this connection it is interesting to note that the Indri- 
sines are diurnal in their habits like most Apes, and that 1m 
ndris the caudal appendage is much reduced in size. 
