Body full and compact; neck short and thick; head large, ovate. Feet short, rather stout; tibia bare for two-twelfths of an inch; tarsus very short, compressed, covered anteriorly with oblique scutella, behind with angular scales; hind toe wanting; anterior toes connected by reticulated webs, the inner much shorter than the outer, which is almost as long as the middle; the scutella numerous. Claws rather small, moderately arched, compressed, rather acute, that of the middle toe having its inner edge considerably expanded. Plumage dense, blended, glossy. Wings of moderate length, narrow, pointed; primaries pointed, the first longest, the rest rapidly graduated; secondaries rounded. Tail very short, slightly rounded, of twelve feathers. Bill black. Iris dark hazel. Feet pale flesh-coloured; webs dusky; claws black. Inside of mouth light yellow. The head, upper part of neck, and all the upper surface, glossy bluish-black. A small spot on the upper eyelid, another on the lower, several longitudinal streaks on the scapulars, and a bar along the tips of the secondary quills, white. The lower parts white; the feathers on the sides under the wings have the outer webs white, the inner dusky; lower wing-coverts blackish-grey. Length to end of tail 7-1/8 inches, to end of claws 7-7/8, to end of wings 6-7/8, to carpal joint 2-7/8; extent of wings 14-1/4; wing from flexure 4-7/8; bill along the ridge (4-1/2)/8, along the edge of lower mandible 1; tarsus 3/4; middle toe 1, its claw 1/4; outer toe 1, claw (1-1/2)/8; inner toe 5/8, its claw (1-1/2)/8. Weight 8-1/2 oz. Adult Female, in winter. Plate CCCXXXIX. Fig. 2. In winter, the throat and the lower parts of the cheeks are white; the sides and fore part of the neck white, irregularly barred with blackish-grey; the upper parts of a duller black than in summer. There is nothing very remarkable in the anatomy of this bird, beyond what is observed in the Auks and Guillemots. The ribs extend very far back, and, having the dorsal and sternal portions much elongated, are capable of aiding in giving much enlargement to the body, of which the internal, or thoracic and abdominal cells are very large. The subcutaneous cells are also largely developed, as in many other diving and plunging birds. The roof of the mouth is flat, broad, and covered with numerous series of short horny papillæ directed backwards. The tongue is large, fleshy, 10 twelfths of an inch long, emarginate at the base, flat above, horny on the back. The heart is large, measuring 10 twelfths in length, 8-1/2 twelfths in breadth. The right lobe of the liver is 1-3/12 inch in length, the left 1-1/12; the gall-bladder is elliptical. The kidneys are very large.