PARTS OF ANIMALS, IV. xm. 



Seals, if regarded as water-animals, are anomalous in 

 having feet ; if regarded as land-animals, in having 

 fins (their hind feet are altogether like those of 

 fishes— I.e. fins ; and all their teeth too are sharp and 

 interlocking). Bats, too, if regarded as birds, are 

 anomalous in having feef* ; if regarded as quadrupeds, 

 in not having feet * ; furthermore, they have neither a 

 quadruped's tail (because they are fliers) nor a bird's 

 tail (because they are land-animals). This their lack 

 of a tail like a bird's is a necessary consequence, 

 since they have membranous wings, and no creature 

 has a tail of this sort unless it has barbed feathers : 

 such tails are always made out of barbed feathers. 

 And a tail of the other sort gro\ving among feathers 

 would be a definite impediment. 



After the same style is the Libyan ostrich: in (m.) The 

 some points it resembles a bird, in others a quadruped. 

 As not being a quadruped, it has feathers ; as not 

 being a bird, it cannot rise up and fly, and it has 

 feathers that are like hairs and useless for flight. 

 Again, as being a quadruped, it has upper eye- 

 lashes, and it is bald in the head and the upper part 

 of the neck, as a result of which its eyelashes are 

 hairier than they would otherwise be ; as being a 

 bird, it is feathered on its lower parts. Also, as 

 a bird, it has two feet ; but, as a quadruped, it has 

 cloven hoofs (it has hoofs and not toes). The reason 

 is that it has the size not of a bird but of a 

 quadruped. Speaking generally, a bird has to be 

 very small in size, because it is difficult for a body of 

 large bulk to move off the ground. 



" That is, of the sort that birds ought not to have, viz. on 

 their wings. 



* That is, of the sort that quadrupeds ought to have. 



429 



