﻿72 ON THE CLASSIFICATION OF BIRDS. 



member among birds. Both mandibles are straight, 

 and so much compressed as to resemble the blade of a 

 knife — placed edgewise — more than any thing else: the 

 upper mandible, indeed, is slightly thickened at its base, 

 where the nostrils are situated ; but one quarter of its 

 length appears broken off, so that the under mandible 

 protrudes beyond the upper nearly an inch {fig, 37.). 



There are three, if not four, species of this most singu- 

 lar genus, which in every other point of structure show r s 

 an intimate affinity to the ordinary Terns. Notwith- 

 standing the length, even of the upper mandible, the 

 mouth of the bird itself is remarkably small : for it 

 does not extend beyond the nostrils. Beyond that part, 

 both the edges on the under mandible are quite sharp, 

 but that which is uppermost is received into a very 

 narrow groove on the corresponding piece, as if to pro- 

 tect and preserve its sharpness. Not having had the 

 opportunity of watching these birds alive, we can state 

 nothing from personal observation ; but this is not to 

 be regretted after the following account of their man- 

 ners by Wilson. 4f The sheer water (Rhynchops niger L.), 

 is formed for skimming, while on the wing, the surface 

 of the sea for its food, which consists of small fish, 

 shrimps, young fry, &c, whose natural haunts are near 

 the shore and towards the surface. That the lower 

 mandible, when dipt into and cleaving the water, might 

 not retard the bird's way, it is thinned and sharpened 

 like the blade of a knife ; the upper mandible, being at 

 such times elevated above water, is curtailed in its 

 length, as being less necessary, but tapering gradually 

 to a point, that, on shutting, it may suffer no oppo- 



