8 CATECHISM OF 



cannot remain constantly beneath the water; their 

 tail, unlike that of the other orders of fish, is 

 horizontal or parallel with the water, and they 

 have only three fins. 



Q. Enumerate the principal genera belonging 

 to this order. 



A. The Balasna, or Whale ; the Physeter ; 

 Cachelot, or Spermaceti Whale ; the Delphinus, 

 or Dolphin ; and the Monodon, or Sea Unicorn. 



Q. What may be observed of the genus Balaena? 



A. Of the Balaena, or Whale, there are several 

 species, as the Mysticetus, black or Greenland 

 whale, Glacialis or Iceland whale, Physalus, or 

 fin fish, so called from its larger dorsal fin, and 

 the Rostrata or piked whale, the smallest of the 

 genus, seldom exceeding twenty-five feet in length. 



Q. Will not a description of the Mysticetus, 

 give a tolerable idea of the whole genera ? 



A. Yes ; it is the largest animal of which we 

 have any authentic account, being sometimes 

 found in the northern seas, ninety feet long, 

 and there is reason to suppose that when unmo- 

 lested and suffered to attain its full age, it greatly 

 exceeds that length. Whales are occasionally 



Dorsal, a. belonging to the back. 



