240 ORDER CETACEA; GENERAL CHARACTERS. 



fibres so closely interwoven and compressed, that it is difficult to 

 cut it with a knife ; and so perfectly adapted to the opening, that 

 not even the enormous pressure just now stated can disturb or 

 injure it, or force a drop of water between its sides, and the tube 

 which it closes. Of the sense of smell, the Whale can possess 

 but little. The aperture of the ear is closed by a similar 

 valve. It appears that, when under water, the Whale can hear 

 the smallest sounds, such as the slightest splash of an oar ; but 

 that to sounds in the air above, even the report of a cannon, it is 

 insensible. 



210. The Cetacea are all carnivorous ; but the nature of 

 their food varies considerably. In some it consists of Fishes ; 

 others seem peculiarly to prefer the Cuttle-fish ; others feed upon 

 the smaller species of their own order ; whilst the Whale, the 

 largest of all, is supported chiefly by minute Mollusks and 

 MedusaB. The teeth vary extremely in the different genera ; and 

 cannot be alone trusted to, as characters for subdividing the order 

 into families. Excluding the MANATIDJE, which, though Whale- 

 like animals, belong to the herbivorous series, and differ from the 

 true Cetacea in many important particulars, we may naturally 

 divide the order into three families. 1 . DELPHINID.E, or Dol- 

 phin tribe, characterised by the moderate size of the head ; and 

 usually by the presence of teeth in both jaws. 2. CATODONTIDJE, 

 the Cachalots or Spermaceti-Whales, characterised by the very 

 large size of the head, which constitutes one-third, or even nearly 

 one-half, of the entire length ; and also by the presence of teeth 

 in the lower jaw. 3. BAL^NIDJE, the Whalebone- Whales, also 

 distinguished by the enormous size of the head, but altogether 

 destitute of teeth. 



211. The family DELPHINID^ includes, with the Dolphin 

 and Porpoise, many animals which are ordinarly called Whales. 

 A large proportion of these are occasional visitants of our own 

 coasts, especially towards the north of Scotland, and off the 

 Orkney and Shetland islands. The teeth are usually numerous ; 

 simple in their structure, and conical in form. The common 

 Porpoise is an active and voracious animal, feeding especially 

 upon fish, and following in the wake of the shoals of Herring and 



