xvii CHARACTERS OF LEMURS 535 



second toe is furnished with a sharp nail, unlike the flattened 

 nails of the other fingers and toes, and in Tarshis 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 lies upon the face in front of the orbit. 

 The teeth are characteristic, not so much in their number (the 

 dental formula is usually 12, C I, Pm 3, M 3 = 36) 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, 1 

 by Milne-Edwards, 2 and by myself. 3 There are also a number 

 of scattered papers dealing with particular types, such as the 

 memoirs of Owen 4 and Oudemans, 5 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 Verli. Ak. Amsterdam, xxvii. 1890, Art. '2. 



