472 LARIN^. 



GENUS II. CETOSPARACTES. WHALE-GULL. 



Bill short, robust, compressed, straight ; upper mandible 

 uith the ridge broadly convex, the nostrils mcdio-basal, 

 linear-oblong, wider anteriorly, covered above and behind 

 •with a sloping thin-edged plate, the edges thin, direct, the 

 tip slightly decurved, obtuse ; lower mandible with the crura 

 somewhat convex, their lower outline straight, forming a very 

 slight prominence at the commissure, the dorsal line ascend- 

 ing, the edges thin and somewhat inflected, the tip narrow, 

 rather obtuse. Legs very short ; tibia bare to a small extent ; 

 tarsus very short, little compressed, covered anteriorly with 

 nearly straight scutella, laterally and behind with very small 

 prominent scales ; hind toe very small, little elevated, with a 

 stout decurved claw ; fore toes short, prominently papillate 

 beneath, the latter thickly margined ; interdigital membranes 

 emarginate ; claws strong, well curved, rather acute. Wings 

 very long, rather broad, pointed. Tail of moderate length, a 

 little rounded. 



1. Cetosparactes ehurneus. Ivory Whale- Gull. The 

 only species. Plumage white. 



GENUS III. RISSA. KITTIWAKE. 



Bill rather short, moderately stout, compressed, nearly 

 straight ; upper mandible with the ridge convex, the nostrils 

 sub-medial, linear-oblong, wider anteriorly, covered above 

 and behind with a sloping, convex, thin-edged plate, the 

 edges thin, direct, the tip slightly decurved, narrow, rather 

 acute ; lower mandible compressed, with the lower outline of 

 the crura slightly concave, forming a slight prominence at the 

 commissure, the dorsal line distinctly concave, and scarcely 

 ascending, the edges thin and inflected, the tip compressed 

 and rather acute. Legs very short ; tibia bare to a moderate 

 extent ; tarsus very short, considerably compressed, covered 

 anteriorly with decurved scutella, laterally and behind with 

 small nearly flat scales. Hind toe extremely diminutive, 

 with a minute claw, obsolete in old individuals ; fore toes of 



