SENEGAL TERN. 251 



fore consider them as distinct, at least until further 

 information proves the contrary. In reference to 

 Mr. Selby's account of the S. hirundo, we shall 

 merely point out in what respects our present bird 

 differs. The bill measures only 1 T 4 5 of an inch from 

 the forehead to the tip, instead of one inch and a 

 half: there are no " long occipital feathers," those 

 of our bird being in no respect lengthened. The 

 under plumage, instead of being pure white, with a 

 tinge of grey only on the breast, is only pure white 

 on the chin, sides of the head, and beginning of the 

 throat; from thence a very slight shade of pearl- 

 grey commences, which gradually increases over 

 the breast, body, and belly, where it is darkest, and 

 where it terminates : the under tail-covers are like 

 the upper, pure white : the wings are slightly longer 

 than the tail, and the colouring of both agrees with 

 Mr. Selby's description ; but the same may be said 

 of two other species now before us, one from the 

 arctic regions, and the other, as supposed, from 

 India. All these have a marked difference in their 

 size, and, with other peculiarities, create a belief 

 that they are specifically distinct. The bill of this is 

 very slender, and more curved than in the others. 



Total length, 12 inches; bill, front, 1 T 4 5 ; gape, 

 2 ; wings, 10, being about f longer than the tail ; 

 tarsus hardly ^ ; middle toe and claw, 1 ; hind 

 ditto, fo ; tail, base, 6 ; depth of the fork, 2 T 7 D ; 

 outer feather 1-fo longer than the others. 



