MAMMALIA 



411 



twenty-four seals off the Pribilof Islands. The black fish reaches 

 a length of about eighteen feet and has been taken in great quantities 

 on account of its valuable jaw oil. It is able to elevate itself ver- 

 tically in the water, standing on its tail. The white " whale " 

 is found in the far North, where it is said to ascend the Yukon River, 

 Alaska, for seven hundred miles. 



Fig. 233. Side view of porpoise at Woods Hole, Mass. (Photo by Julian Scott.) 



Fossil Relatives of the Cetacea. — Certain primitive Eocene 

 whales seem transitional from early Carnivora. The toothed whales 

 are found in the Middle Tertiary, and the sperm whales appeared 

 in the Upper Eocene. Whale-bone whales are known from the 

 Miocene to the present. 



Order Primates. (Lemuroidea, Anthropoidea, Hominidae.) — 

 The Primates include the Old and New World monkeys and the 

 most highly developed Primate — man. For the most part the 

 Primates inhabit a warm climate. Chiefly arboreal in habits, we 

 find that with the exception of man, they feed on fruit, insects and 

 birds, and do not engage in the chase after terrestrial prey. 



Characteristics. — Primates have from 32 to 36 teeth, a closed 

 orbit, and two pectoral mammae. They excel in the development of 

 the nervous system, having large richly convoluted cerebral hemi- 

 spheres, but are comparatively primitive when bones, muscles, 

 teeth, and other organs are taken into account. Nearly all are 

 adapted to an arboreal life; the limbs are prehensile owing to the 

 pollex and hallux being more or less completely opposable to the 

 other digits. There are nearly always five nailed digits. Clavicles 

 are well developed. They have no foramen above the inner condyle 

 of the humerus and the femur rarely has a third trochanter. The 



