210 BLA€K SKIMMER. 
mandible 43; depth of bill at the base 1; wing from flexure 15% ; tail 
to the fork 33; to end of longest feather 51; tarsus 11; hind toe and 
claw 7‘; middle toe }$; its claw 74. Weight 13 oz. 
The female, which is smaller, is similar to the male, but with the 
tail-feathers white, excepting a longitudinal band including the shaft. 
Length to end of tail 16%, to end of wings 20}, to end of claws 164, 
to carpus 8; extent of wings 443. Weight 10 oz. 
After the first autumnal moult, there is on the hind part of the neck 
a broad band of white mottled with greyish-black ; the lower parts 
pure white, the upper of a duller black; the bill and feet less richly 
coloured. 
Length to end of tail 16} inches, to end of wings 20, to end of claws 
143, to carpus 63; extent of wings 42. 
In some individuals at this period, the mandibles are of equal 
length. 
The palate is flat, with two longitudinal series of papille directed 
backwards. The upper mandible is extremely contracted, having inter- 
nally only a very narrow groove, into which is received the single thin 
edge of the lower mandible. The posterior aperture of the nares is 1,5, 
inch long, with a transverse line of papille at the middle on each side, 
and another behind. The tongue is sagittiform, 64 twelfths long, with 
two conical papillz at the base, soft, fleshy, flat above, horny beneath. 
Aperture of the glottis 43 twelfths long, with numerous small papille 
behind. Lobes of the liver equal, 14 inch long. The heart of mode- 
rate size, 1; long, 10 twelfths broad. 
The cesophagus, of which only the lower portion, a, is seen in the 
figure, is 8 inches long, gradually contracts from a diameter of 1 inch 
to 4 twelfths, then enlarges until opposite the liver, where its greatest 
diameter is 174. Its external transverse fibres are very distinct, as 
are the internal longitudinal. The proventriculus, 6, is 9 twelfths 
long, its glandules extremely small and numerous, roundish, scarcely 
a quarter of a twelfth in length. The stomach, ¢, d, e, is rather small, 
oblong, 1 inch 4 twelfths long, 11 twelfths broad, muscular, with the 
lateral muscles moderate. The cuticular lining of the stomach is dis- 
posed in nine broad longitudinal ruge of a light red colour, as in the 
smaller Gulls and Terns. Its lateral muscles are about 4 twelfths thick, 
