TERNS AND ALLIED SPECIES. 623 



1. Steriia velox. RuppelVs Tern. Bill yellowish-horn- 

 colour ; feet black ; tarsus an inch long ; tail and wings 

 about equal. 



2. Sterna Cantiaca. Sandwich Tern. Bill black, with 

 the points yellowish ; feet black, with the soles yellow ; 

 tarsus an inch long ; tail shorter than the wings. 



3. Sterna Hirundo. Common Tern. Bill rather slender, 

 coral-red, black at the end ; feet red ; tarsus about ten- 

 twelfths long ; tail about the same length as the wings. 



4. Sterna arctica. Arctic Tern. Bill slender, vermilion ; 

 feet crimson ; tarsus about six-twelfths long ; tail about half 

 an inch longer than the wings. 



5. Sterna Dougallii. Roseate Terti. Bill slender, black, 

 at the base orange-red ; feet vermilion ; wings about three 

 inches shorter than the tail. 



6. Sterna minuta. Little Tern. Bill light orange-yellow, 

 with the tip black ; feet light orange-red ; wings an inch 

 longer than the tail. 



GENUS III. HYDROCHELIDON. MARSH-TERN. 



Bill about the length of the head, nearly straight, slender, 

 compressed, tapering, with the edges sharp, and the tip 

 elongated and pointed ; the upper mandible with its outline 

 gently arcuatie, the lower with the junction of the crura 

 mesial ; legs very short, slender ; anterior toes small, their 

 membranes deeply emarginate ; wings very long and acumi- 

 nate ; tail of moderate length, emarginate. 



1. Hydrochelidon nigra. Black Marsh- Tern. Bill black; 

 feet dark reddish-brown ; tail about two inches shorter than 

 the wings ; head, neck, breast, and abdomen greyish-black ; 

 upper parts dark bluish-grey. 



2. Hydrochelidon leucoptera. White -winged Marsh- 

 Tern. Bill reddish-brown; feet coral-red; tail about two 

 inches and a half shorter than the wings ; head, neck, fore 

 part of breast and abdomen black ; upper wing-coverts, 

 rump, tail, and its coverts white. 



3. Hydrochelidon leucopareia. Whiskered Marsh-Tern. 

 Bill rather stout and, with the feet, red; tail about two 



