Length to end of tail 16 inches, to end of claws 14-1/4, to end of wings also 14-1/4; extent of wings 31-1/4; wing from flexure 7-4/12; tail 3-5/12; bill along the back 1-1/4, from frontal process to tip 1-1/2; tarsus 1-2/12; first toe and claw 5/12; middle toe and claw 1-10/12; outer toe and claw 1-8/12. Weight 12-1/2 oz. Adult Female. Plate CCCXIII. Fig. 2. Bill greenish-dusky; iris hazel; feet of a duller yellow than those of the male, the head and neck are pale dull buff, longitudinally marked with brownish-black lines, which are broader and darker on the top of the head; the fore part of the cheeks and the throat whitish, without markings. The upper parts are dark brown, the feathers margined with brownish-white; the smaller wing-coverts coloured as in the male, but less brilliantly; no blue on the scapulars, which are also less elongated. On the lower parts, the feathers are dusky brown, broadly margined with light brownish-grey, of which there is a streak or spot in the centre. The axillary feathers, and some of the lower wing-coverts are white, but the patch of that colour so conspicuous in the male is wanting. Length to end of tail 15 inches, to end of wings 14-1/2, to end of claws 15-1/2; extent of wings 24; wing from flexure 7-1/4; tail 2-7/12; bill along the ridge 2-2/12. Weight 10-1/2 oz. The young birds are similar to the female, but paler, and without the green speculum. In a male, the roof of the mouth is deeply concave, with a prominent middle ridge, on which are a few blunt papillæ; on the upper mandible are 50 lamellæ, on the lower about 65 below, and 85 above. The tongue, 8 twelfths long, large and fleshy, has two rows of lateral bristles. The œsophagus is 8-1/2 inches long, 4 twelfths in diameter until the middle of the neck, when it enlarges gradually to half an inch. The proventriculus is 1-1/4 inch in length, with oblong glandules. The stomach is a strong roundish gizzard, 1 inch and 2 twelfths long, 1-1/2 inch broad; its left muscle 7 twelfths thick, the right 6-1/2 twelfths; its cuticular lining or epithelium of moderate thickness and longitudinally rugous. The intestine, 5 feet 1 inch long, varies in diameter from 3 to 2 twelfths; the cœca are 2 inches 10 twelfths long, cylindrical and rounded, their diameter 3 twelfths; the cloaca globular. The contents of the stomach were gravel and seeds of plants. The trachea is 6 inches and 2 twelfths long; its diameter at the top 4 twelfths, at the middle 2 twelfths, at the lower part 3-1/2 twelfths. The inferior larynx is formed of three or four united rings, and has an irregular roundish bony expansion on the left side. The number of rings of the trachea is 98, of the bronchi about 25. The contractor muscles are large; cleido-tracheales and sterno-tracheales. BLACK-HEADED, OR LAUGHING GULL. _LARUS ATRICILLA_, LINN. PLATE CCCXIV. MALE IN SPRING, AND YOUNG.