618 ZOOLOGY. 



Order XII. Primates. — The last and highest order of 

 mammals contains a series beginning with creatures resem- 

 bling squirrels and bats, i. e., the lemurs, and comprising 

 monkeys, apes, and ending with man. In all the Primates, 

 the legs are exserted almost or quite free from the trunk, 

 with the great toe of the hind foot usually enlarged and op- 

 posable to the others ; nails, except in the marmosets, replace 

 claws ; the teeth are usually of the following formula : 



^3-3' ^1-1- ^3:13' "^3-3' 

 with one exception canine teeth are always present ; the pre- 

 molars are usually n^;^, but in the American monkeys ^^. 



The hemispheres of the brain may in the lower forms be 

 quite smooth, but in all there is a well-developed "calcarine 

 furrow," giving rise to a " hippocampus minor" within the 

 posterior cornu of the ventricle, by which the posterior lobe 

 of the cerebrum is traversed (Flower). The collar-bones 

 (clavicles) are for the first time in the series well developed. 

 The placenta is also different in shape from that of other 

 mammals, being disk or cake-like, but in lemurs it is "diffuse." 



The Primates are divided into two sub-orders, i. e., the 

 ProsimicB and Anthropoidea. The former group embraces 

 the lemurs, which vary in size from that of a rabbit to a 

 large monkey. They are covered, the face as well as the rest 

 of the body, with a dense fur ; walk on all-fours, usually 

 have long tails, though the lori is tailless, while the fore 

 limbs are shorter than the hind limbs. The skull is small, 

 flattened, and narrow in front ; the brain-cavity small in 

 proportion to the rest of the skull, i. e., the face compai-ed 

 with the monkeys. The cerebral hemispheres are small and 

 flattened, the frontal lobes narrow and pointed, and behind 

 they only slightly cover the cereoellum. 



By some authors the lemurs are separated from the Pri- 

 mates, the Insectivora and Cheiroptera being placed between 

 the ProsimicB and the other Primates. They have characters 

 in which they resemble Insectivora, Rodentia, and Carnivora, 

 but the weight of organization, or the sum of their charac- 

 ters, ally them nearest to the monkeys. They are therefore 

 essentially a generalized or ancestral type. Eecent discov- 



