CETACEANS. 



591 



The largest bats are the fruit bats or flying foxes {Ptero- 

 yus) of the East Indies ; one species of which expands one 

 -and a half metres (nearly five feet) from tip to tip of the 

 wings. Our commonest species is 

 the little brown bat, Vespertilio 

 subulatus of Say ; nearly as com- 

 mon is the red bat, Atalapha no- 

 veboracensis Coues. 



Order 5. Cete {Cetacea). — We 

 now come to the Educalilia, in 

 Tvhich the brain is more highly de- 

 veloped, and begin with two very 

 -aberrant orders, the whales and 

 Sirenians, in which the body is 

 fish-like, though the tail is hori- 

 zontal ; the pelvis and hind limbs 

 are wanting, either wholly, or mi- 

 .nute rudiments may be present ; 

 -and they are aquatic, occasionally 

 leaping out of the water, but usu- 

 ally only showing the dorsal fin or 

 nose when at the surface to breathe. 



The whales and porpoises have 

 a large, broad brain, with numer- 

 ous and complicated deep convolu- 

 tions. 



In the skull (Figs. 512, 513) the 

 aperture for the spinal cord {fora- 

 men magnimi) is entirely posterior 

 in situation and directed some- 

 Tvhat upward. The lower jaw is 

 .straight, with no ascending ramus, 

 the narrow condyles being situated 

 .at the end of the jaw, at the point 

 indicated by the angle of the ramus 

 in other mammals. The teeth are 

 conical, with a single root, but are 

 sometimes wanting. There is no neck 



Fig. 513.— Skull of the sperm 

 whale, longitudinal section anow- 

 mg the relative size and form of 

 the cranial cavity, m, maxilla ; 

 pm, premaxilla.— After Flower. 



the cervical verte- 



LrsB are sometimes confluent, forming a single mass. The 



