Section B. P INN AT A. 



Seals, Dugongs, and "Whales, the living representatives of the 

 Pinnata, although they differ greatly in many essentials of structural 

 character and external form, appear nevertheless to constitute a very 

 compact sectional group, being intimately allied not only by the 

 several usually recorded features of similarity, progressively exhibited 

 by a series of transitional links, but likewise, and that impressively, 

 by the possession in common of a peculiarity of organisation, unknown 

 to any other of the Mammalian Orders, with a solitary exception. 



The following comparative details will serve to illustrate the former 

 assertion, but the restricted nature of this treatise permits me no 

 license in this, as well as in other cases, to diverge into anatomical 

 particulars, beyond the simple allusion to the existence of the latter ; 

 it being imperative to refer to the fact, in order to sustain, by its 

 additional contribution, the validity of the present deviation from the 

 beaten track, in allying, so immediately, the Pinnipedia with the Sirenia 

 and Cetacea. 



The transition, apparently so incongruous, from the purely terres- 

 trial quadrupeds to such mammals as the Dugong and the "Whale, 

 whose hinder members are defective, and whose lives are rigorously 

 restricted to the waters, is effected through the medium of the semi- 

 aquatic carnivorous animals, the Sea Otter, the last erratic represen- 

 tative of the land flesh-eaters, and the Sea Bears, the first of the series 

 of the present section. 



The lengthened fur-covered body, the shortened limbs, still capable 

 of being used for progression on land, the palmated and unguiculated 

 feet, the small, somewhat depressed tail, the oceanic habits, thb 

 similarity of food, and mode of capture, and the process of mastica- 

 tion commonly above the surface of the water, when considered in 

 the aggregate, attest the affinity of the Sea Bear to the Sea Otter in 

 sufficiently marked characters, however greatly each separate function 

 may be modified under the varying conditions of their existence. 



Then, by the more elongated form of the Phocidae propriae, by the 

 nearly immovable condition of their hinder limbs, which stretch 

 rigidly backwards almost in a line with the body, the broad webbed 

 feet being capable only of lateral free motion for the purpose of pro- 

 pulsion through the water, and by the external position of the nostrils 

 at the end of the muzzle, the animals of the order Pinnipedia 

 approach those 'of Sirenia. 



The Manatee, Dugong, and the Rhytina, in possessing horizontal, 

 cartilaginous, tail-like, hinder extremities, in having the nasal aper- 

 tures placed high up on the skull, although the nostrils terminate at 

 the extremity of the face, in many other portions of their structural 

 character, and in their wholly aquatic existence, graduate so 

 naturally into the whale-tribe, as to have caused Cuvier to term 

 them the herbivorous Cetacea. 



