THE RED-THROATED DIVER 
187 
Adult Male in summer. 
Bill as long as the head, slender but strong, straight, rather compressed, 
tapering to a point. Upper mandible with the dorsal line almost straight, 
the ridge convex, as are the sides, the edges sharp and involute ; nasal groove 
basal, short ; nostrils basal, lateral, direct, oblong, pervious. Lower man- 
dible with the angle extremely narrow and extending beyond the middle, 
the dorsal line straight and sloping upwards to the point, the ridge convex, 
but narrower than that of the upper mandible, the edges sharp and involute ; 
the point of both mandibles rather sharp. 
Head of moderate size, oblong, narrowed before. Neck rather long and 
slender. Eyes rather small. Body elongated, somewhat depressed. Wings 
small. Feet short, rather large, placed very far back ; tibia almost entire- 
ly concealed ; tarsus short, exceedingly compressed, sharp-edged before and 
behind, covered all over with reticulated angular scales ; hind toe extremely 
small, connected with the second by a very small membrane ; the anterior 
toes united by reticulated membranes, the fourth longest, the third a little 
shorter, the second considerably shorter than the third ; all covered anteri- 
orly with very narrow transverse scutella, the second toe with a free two- 
lobed membrane ; claws very small, depressed, rounded. 
Plumage short and dense ; of the head and neck very short, blended ; of 
the lower parts blended, short, and with a silky gloss ; of the upper slightly 
glossed and somewhat compact ; the feathers in general oblong and rounded. 
Wings proportionally very small and narrow, curved ; primaries strong, 
tapering, first longest, second almost as long, the rest rapidly graduated ; 
secondaries broad, rounded. Tail extremely short, rounded, of twenty 
rounded feathers. 
Bill bluish-black. Iris deep bright red. Feet brownish-black, the ante- 
rior- edge of the tarsus, the upper surface of the toes, the claws, and part of 
the webs, pale livid flesh-colour. Fore part and sides of the head, throat 
and sides of the neck, of a fine bluish-grey ; fore part of the neck rich 
brownish-red ; hind part of the head and hind neck longitudinally streaked 
with greenish-black and pure white, each feather black in, the middle, with 
the sides white, the colours disposed in lines. The upper surface brownish- 
black, tinged with green, more or less mottled with white according to age, 
excepting the primary quills and the tail-feathers, the latter of which are 
merely paler at the end. The whole under surface pure white, excepting 
the feathers on the sides under the wings, some of those about the vent, and 
the lower tail-coverts, which are greyish-brown, with white margins and tips. 
Length to end of tail 254 inches, to end of claws 27 ; extent of wings 
43 r V ; bill 2 T 2 2 ; gap 3f ; tarsus 3 ; fourth toe and claw 31 ; wing from flex- 
ure 111 ; tail 3. Weight 4 lbs. 
