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COLYMBIN^ COLYMBUS. 
webs, which in some are lobed. Plumage dense, shorty 
glossy, generally silky beneath. Wings small, very narrow, 
acute. Tail very short, sometimes extremely small, and 
forming a slight tuft. Tongue slender, trigonal, tapering; 
oesophagus very wide in its whole length, or narrowed in 
the anterior part with the proventriculus wide ; stomach 
generally large, muscular, with a dense rugous epithelium ; 
intestine rather long and wide ; as are the coeca ; cloaca 
globular. 
GENUS I. COLYMBUS, Linn. DIVER. 
Dill as long as the head, straight, rather stout, much com- 
pressed, tapering, pointed ; upper mandible with the dorsal 
line descending, and slightly convex towards the end, the 
ridge convex, narrowed towards the point, the sides nearly 
erect, convex, the edges sharp and considerably inflected ; 
the tip narrow ; nasal groove rather long, feathered at the 
base. Nostrils basal, linear, direct, pervious ; lower mandi- 
ble with the angle extremely narrow and extending beyond 
the middle, the dorsal line straight and sloping towards the 
point, the ridge convex and narrow, the edges sharp and 
involute, the tip attenuated. Head of moderate size or 
rather large, oblong, narrowed before ; neck rather long 
and thick; body elongated, much depressed. Feet short, 
rather large, placed very far back ; tibia almost entirely 
concealed ; tarsus short, exceedingly compressed, sharp- 
edged before and behind, covered all over with reticulated 
scales ; toes four, hind toe extremely small, connected with 
the second by a very small membrane ; anterior toes united 
by entire membranes, the outer longest, the third a little 
shorter, all scutellate. Claws very small, depressed, blunt. 
Plumage short and dense, the feathers in general oblong. 
Wings very small and narrow, curved, first quill longest, 
secondaries broad and rounded. Tail extremely short, 
