XVII CHARACTERS OF LEMURS 5 
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second toe is furnished with a sharp nail, unlike the flattened 
nails of the other fingers and toes, and in Varsius the third also 
is thus provided. As to osteology, the shape of the head, already 
referred to, indicates some of the differences in the skull which 
mark off the Lemurs from the Anthropoidea. The brain case is 
small relatively to the face; the orbital and temporal fossae are 
in communication, though the frontal and jugal bones are united 
behind the orbit. The two halves of the lower jaw are not in- 
variably ossified to form one piece, as is the case with most Apes. 
The lachrymal foramen hes upon the face in front of the orbit. 
The teeth are characteristic, not so much in their number (the 
dental formula is usually 12, C1, Pm3,M3=836) as in the 
disposition of the incisors. The incisors of the lower jaw and the 
canines project forwards in a way only found in a few American 
Monkeys; as in the Apes there are four incisors in each jaw, but, 
with the exception of the highly aberrant Chiromys, there is a 
space in the upper jaw between the incisors of the two sides. 
The canines of the lower jaw, moreover, are often incisiform. 
There is a well-developed sublingua beneath the tongue (see p. 61). 
The stomach is perfectly simple; and the caecum, always present 
and varying in length, never has a vermiform appendix. The 
gall-bladder is always present. The brain differs from that of 
the Anthropoidea in that the cerebellum is, as in the lower 
Mammalia, exposed. The convolutions upon the cerebral hemi- 
spheres are not greatly developed, a circumstance, however, which 
(see p. 77) may have more relation to the size of the animals 
than to their mental development. Though the brain in its 
general outlines is not like that of the other Primates, there are 
certain resemblances; the most striking of these is perhaps the 
presence, though in rather a rudimentary condition, of the “ Simian 
fissure.” 
The Lemurine brain has been chiefly studied by Flower,’ 
by Milne-Edwards, and by myself. There are also a number 
of scattered papers dealing with particular types, such as the 
memoirs of .Owen* and Oudemans,’? upon the brain (and the 
general anatomy) of Chiromys. Without going into great 
1 Trans. Zool. Soc. v. 1863, p. 103. 
2 Hist. Nat. de Madagascar, Mamm. 1875. 
3 Proc. Zool. Soc. 1895, p. 142. 
4 Trans. Zool. Soc. v. 1863, p. 33. 
5 Verh. Ak. Amsterdam, xxvii. 1890, Art. 2. 
