THE SIMIADiE. 391 



»r longitudinal crescents. The cusps of the molars are usually 

 much produced, as in the Insectivora. 



In the Gheiromyini, the pollex is not truly opposable, and 

 its naU is claw-like and resembles that of the other digits. 

 All the digits of the pes, except the hallux, have compressed, 

 claw-like nails. The middle digit of the manus is much more 

 slender than atfy of the others, and is longer than the fourth. 

 The long axis of the articular head of the mandible is antero- 

 posterior. The dentition differs from that of all the other 

 Lemurs (and indeed from that of all the other Primates), and 

 resembles that of the Rodents. 



Thus there is only one pair of incisors in each jaw,* and 

 these grow from persistent pulps and have a thick layer of 

 enamel on their anterior faces, whence they wear to sharp 

 chisel-edges, like the incisors of the Modentia. No canines 

 are developed, and there are four grinders with simple crowns 

 on each side above and below. 



The formula of the milk dentition is d.i. ^r-j d.c. J^ d.m. j4|. 



The JLemuridcB are confined to Eastern Asia, Madagascar, 

 and South Africa ; Madagascar presenting the greatest num- 

 ber and diversity of genera and species. 



b. In the great group of the Simiadm, which contains the 

 Apes and Monkeys, the attitude is sometimes habitually quad- 

 rupedal, the axis of the body being horizontal ; but, in a few 

 species, the trunk is habitually held in a more inclined posi- 

 tion, and the animals readily assume the erect attitude. 



The Simiadce are sometimes terrestrial in habit, and good 

 runners, but they are always excellent climbers, and, in some 

 oases, they are necessitated by their organization to be almost 

 as thoroughly arboreal as the Sloths. 



The hallux is always much shorter than the second digit 

 of the foot, and capable of very free movement in adduction 

 and abduction. 



The series of the teeth, in each jaw, is interrupted by a 

 diastema in front of the canine in the upper jaw, and behind 

 it, in the lower ; and the canine teeth are longer than the oth- 

 ers, the points of their crowns projecting for a greater or less 

 distance beyond the rest. 



In the skull, the length of the basi-cranial axis equals more 

 than half the extreme length of the cavity which contains the 



* Among the Lemuridce, the outer and upper incisors of Nijcticebus and 

 Tardus soon fall out. Ziehanotm and Tarsim have only one pair of incisors 

 in the mandible. 



