430 CLASS MAMMALIA. 



their offspring, and all the details of their anatomy, 

 sufficiently distinguish them from the class of 

 fishes. 



The brain is ample, and its hemispheres well 

 developed. That part of the cranium which con- 

 tains the external ear is separated from the rest of 

 the head, and only adheres to it by means of liga- 

 ments. The ears are not externally protuberant, 

 nor are there hairs upon the body. 



The form of their tail obliges them to wave it up 

 and down in swimming, and is of great assistance 

 in enabling them to elevate themselves in the water. 



We shall add to the genera hitherto reckoned 

 among the Cetacea, those which were formerly 

 confounded with Trichecus : they form our first 

 family, or 



The Herbivorous Cetacea. 



Their teeth have flat coronals, a character which 

 determines their mode of existence. Accordingly 

 they frequently emerge from the water to seek for 

 pasture on the shore. They have two mammse on 

 the breast, and hairs like mustachios, two circum- 

 stances which, when they raise the anterior part 

 of the body above water, give them some re- 

 semblance to men and women, and have pro- 

 bably occasioned those fables of the ancients 

 concerning tritons and sirens. Though in the cra- 

 nium the osseous part of the nostrils opens towards 

 the top, yet the opening in the skin is at the termi- 

 nation of the muzzle. 



