TERNS. 401 



and shed by various means in the sea, and it has but little 

 tendency to coine to the land. It does not appear that 

 fishes, from their structure, can feed upon it ; and there- 

 fore, if there were not birds for that purpose, it would be 

 lost. To collect it is not the business of the terns, but 

 the business of those which live farther from the land, and 

 are better adapted than are the terns for this species of food 

 and the necessary mode of feeding. Of them we shall have 

 to give a short hint by-and-by. 



The generic characters of the terns are the bill as long 

 as the head or longer, slender, nearly straight, compressed, 

 sharp in the cutting edges, pointed at the tip, at which 

 the upper mandible slopes down a little ; the nostrils lon- 

 gitudinally cleft about the middle of the bill, and open ; 

 the feet small, the tarsi short, and the tibia naked for 

 some distance above the joint j the wings very long and 

 pointed, and the tail sometimes much produced and forked, 

 at other times of moderate length. The form of the body 

 varies a little, but in general it is that which has been 

 already described as the best adapted for getting through 

 the air firm at the shoulders, and tapering backwards. 

 That form is connected with the development of large 

 muscles for giving powerful motion to the wings ; but it 

 requires that the muscles of the legs should be correspond- 

 ingly small, and hence birds which have it most, use the 

 wing chiefly in their motions, and do not walk or swim 

 much, which requires the moving apparatus of the legs and 

 feet to be more powerful. 



Though the generic characters of the terns are too obvious 

 and well-defined for occasioning the least danger of their 

 being confounded with birds of any other genus, yet the 

 specific difference in appearance, and also in haunt, habit, 

 and geographical distribution, are considerable. 



VOL. II. 2 D 



