450 ZOOLOGY 



SECT. 



sented, and, though there may be numerous pre-molars and molars, 

 these never form roots and are devoid of enamel. All, with the 

 exception of two genera, are monophyodont. The sacral vertebrae 

 are frequently in excess of the number usual in other orders. The 

 coracoid process is usually relatively larger than in other Eutheria, 

 and does not become completely fused with the scapula. The 

 brain is sometimes of low, sometimes of comparatively high 

 organisation. 



There are five families comprised in the order, each characterised 

 by the presence of a number of remarkable peculiar features, viz., 

 the Sloths (Bradypodidce) the American Anteaters (Myrmecopha- 

 gidoe) the Armadillos (Dasypodidce) the Scaly Anteaters (Manidm) 

 and the Cape Anteaters (Orycteropodidce). 



ORDER 2. CETACEA. 



Aquatic Eutheria with large head, fish-like fusiform body, 

 devoid of hairy covering, with the pectoral limbs paddle-like, the 

 pelvic limbs absent, and with a horizontal caudal fin. A vertical 

 dorsal fin is usually present. There is a long snout and the 

 nostrils open by two lateral external apertures or a single median 

 one situated in all the recent forms far back towards the summit 

 of the head. The cervical region of the spinal column is very 

 short, and its vertebrae usually completely united together. 

 Clavicles are absent. The humerus is freely movable at the 

 shoulder, but all the other articulations of the limb are imperfect. 

 The phalanges of the second and third digits always exceed in 

 number the number (three) normal in the Mammalia. The pelvis 

 is represented by a pair of horizontally placed styliform vestiges 

 of the ischia. Teeth may be absent and their place taken by 

 sheets of baleen or " whalebone " ; when present they may be very 

 numerous and homodont, or less numerous and heterodont, or 

 reduced to a single pair. The epiglottis and arytenoids are 

 prolonged, and embraced by the soft palate, so as to form a 

 continuous tube for the passage of the air from the nasal cavities 

 to the trachea. The brain is large, and the cerebral hemispheres 

 are richly convoluted. The testes are abdominal. The teats are 

 two, and are posterior in position. The uterus is two-horned, the 

 placenta diffuse and non-deciduate (vide infra). 



This order includes the Baleen Whales (Balamida:), Sperm 

 Whales (Physeter), Killers (Oreo), Porpoises (Phoccc-na), and 

 Dolphins (Delphinus). 



Sub-order a. Archceoceli (Zeuglodonta). 



Extinct Cetacea in which the premaxillae take a considerable 

 share in the formation of the elongated rostrum, and in which the 

 nasals are long and narrow and the nostrils comparatively for 



