1464 



CLASS MAMMALIA. 



no entepicondylar foramen to the humerus, nor a third trochanter 

 to the femur. The terminal phalangeals of the digits are flattened. 

 In the soft parts there is a discoidal placenta, as in the Insectivora. 

 In our present state of knowledge, it is difficult to draw a line 

 between the more generalised fossil representatives of this order 

 and the Insectivora. Some remarks on the probable origin of the 

 Primates have been already made under the head of the last-named 

 order, while others are added below. 



Suborder i. Lemuroidea. — The existing members of this 

 group differ in many respects from the following suborder, but at- 

 tention may be directed mainly to certain osteological and dental 



characters. Thus the 

 skull (fig. 1347) has 

 a somewhat produced 

 muzzle ; the orbits are 

 not closed behind by 

 bone, but open freely 

 beneath the post-orbital 

 bar into the temporal 

 fossa ; and the lachry- 

 mal foramen is situated 

 on the outer surface of 

 the skull, instead of with- 

 in the orbit. The nostrils 

 have a peculiar twist on 

 the outer side. The incisors vary much in the different families, 

 but they are frequently separated in the middle line, and are usually 



- in number, although they are reduced to - in Chiromys ; those of 

 2 1 



the lower jaw being frequently procumbent. Canines are present 

 except in Chiromys. The number of premolars varies from 



1 in Chiromys to - in the extinct Adapis, but is generally either 

 o 4 



2 or ^ ; while frequently the second lower premolar is larger than 

 2 3 



either of the following teeth. The outer tubercles of the upper true 

 molars (fig. 1349) are laterally flattened, while the inner ones form 

 imperfect crescents ; and in the lower molars the tubercles like- 

 wise form a pair of imperfect crescents. The second digit of the 

 pes has a long claw-like nail, but all the other digits have nails ; the 

 digits themselves being five in number, and the long pollex being 

 generally opposable. The brain has but few convolutions, and the 

 cerebellum is only partially covered by the cerebrum. 



Many of the foregoing characters are common to other orders, 



Fig. 1347. — Left lateral aspect of the skull of the Slow 

 Loris (Nycticebus tardigradus) ; from the Malayan re- 

 gion. The tusk-like tooth in the lower jaw is the second 

 premolar. (After Giebel.) 



