554 



CETACEA. 



strikingly small and are often 

 placed near the angle of the 

 mouth. They are without a 

 third eyelid. The upper and 

 lower eyelids have usually but 

 little motion ; the lacrymal 

 gland is small or absent, and 

 there is no lacrymal duct. 

 The nasal apertures (spiracles) 

 are on the forehead, as the 

 single or double blow-hole. 

 The anterior limbs are repre- 

 sented by short, externally un- 

 jointed flippers, which can only 

 be moved as a whole, and are 

 without or with but the faint- 

 est traces of nails. The digits 

 are entire and enclosed in the 

 common integument, and the 

 number of phalanges tends to 

 exceed that normally found 

 in mammals. There are no 

 external hind limbs, though it 

 appears that vestiges of them 

 are present in the foetus. The 

 bones are spongy in texture 

 and contain oil. The brain 

 case is large, though small as 

 compared with the large facial 

 part, of the head ; it is spher- 

 oidal in form, and often asym- 

 metrical, the right side being 

 the larger. Its bones are sep- 

 arated by sutures and loosely 

 connected. The supraoccipital 

 (Fig. 286) is large and extends 

 by its interparietal portion as 

 far as the frontal, pushing aside 

 the small parletals, which early 

 fuse with the interparietal. 



