MAMMALIA. 



645 



generation : tlie caudal vertebrse are, however, distinguishable 

 by the inferior spinous processes, developed from their under 

 surfaces. As to the construction of the anterior extremity, the 

 shoulder is composed of the scapula alone. The arm and fore-arm 

 are much stunted, and are not moveable at the elbow ; therefore the 

 muscles for pronating and supinating the arm do not exist, but are 

 represented by aponeurotic expansions spread over the surfaces of 

 the bones. The bones of the carpus are flattened, and more or 

 less consolidated together. The fingers, likewise, are flat; and the 

 whole limb so covered with tendinous bands, and enveloped in skin, 

 as to form merely a fin, whereby the creature guides its course 

 through the water. 



(725.) In the Herbivorous Cetacea, as the Manatus and Du- 

 gong, the head is smaller in proportion to the sides of the body, 

 and the hands better developed, so as to be useful in creeping 

 on land, or in carrying their young. These genera inhabit the 

 mouths of tropical rivers. 



(726.) The relationship between the Cetacea and the next order 

 that offers itself to our notice is too evident not to be immediately 

 appreciated. The thick and naked skin, the gigantic body, 

 the massive bones, the bulky head, and even the variable and 

 irregular teeth that arm the ponderous jaws, are all again conspi- 

 cuous in the PACHYDERMATA; and the river and the marsh, the 

 localities frequented by the latter, as obviously indicate the inter- 

 mediate position which these animals occupy between the aquatic 

 and the terrestrial Mammalia. 



Ffc. 300. 



