SLENDER-BILLED GUILLEMOT. 
163 
lower mandible 1 T L ; wing from flexure 5 r \ ; tail 1 T 2 ^ ; tarsus ; middle 
toe its claw f|. 
Two other individuals, apparently more advanced, or perhaps adults in 
winter, have the upper parts brownish-black ; the lower white but finely 
mottled, a small portion of the extremity of each feather being greyish- 
dusky. The white bands on the hind neck aud scapulars are formed, and 
the lower surface of the wing is brownish-grey. 
FAMILY XLY. — COLYMBINiE. DIVERS AND GREBES. 
Bill of the length of the head, straight, rather stout, much compressed, 
pointed ; upper mandible with the dorsal line decimate, almost straight, or 
towards the end convex ; nasal groove rather long, feathered at the base. 
Nostrils basal, linear, direct, pervious. Feet stout, short, placed extremely 
far behind ; tarsus extremely compressed ; toes four, the first very small, and 
lobed ; the anterior united by webs, which in some are lobed. Plumage 
dense, short, 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 : intes- 
tine rather long and wide ; as are the cceca ; cloaca globular. 
