ANTERIOR LIMBS OF BIRDS, ETC, 73 



When at the full stretch, this expansion serves 

 as a parachiite, enabling the little creatures to 

 take long skimming leaps from branch to 

 branch, or tree to tree, like the flying squirrels, 

 or the flying opossums of Atistralia. The 

 contrivance is not to render them aerial, but 

 more thoroughly arboreal in their habits. 

 Although none of the reptiles of the present 

 day are formed for winging their way through 

 the air, many are adapted for the water, and 

 have their limbs constructed for moving in the 

 water, as Ave see strikingly exemplified in the 

 marine tortoises or turtles, to which we have 

 previously made allusion. In these animals, 

 the flattened form of the body, and the extent 

 of their compressed paddles, harmonize with 

 each other very palpably, and. combine to ren- 

 der every movement in the water prompt and 

 easy. On the sandy shore, whither the turtle 

 resorts for the purpose of depositing the eggs, 

 its movements are awkward in the extreme; 

 it shuffles along in the manner of a seal, forcing 

 itself onward by reiterated strokes of its large 

 paddles against the sand, but the moment it 

 gains the water this toilsome method of making 

 its way is over ; it swims and dives, and 

 ploughs the waves with infinite address; and 



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