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.
Fig. 1.
Fig. 2.
Fig. 3.
The œsophagus, Fig. 1, a b c, is 3 inches 10 twelfths long, its walls very thin, its inner or mucous coat thrown into longitudinal plates; its diameter at the middle of the neck 5 eighths, diminishing to 4 twelfths as it enters the thorax. It then enlarges and forms the proventriculus, c e, which has a diameter of 8 twelfths; the glandules are cylindrical, very numerous, and arranged in a complete belt, half an inch in breadth, in the usual manner, as seen in Fig. 2, b c. The stomach, properly so called, Fig. 1, d g, is oblong, 11 twelfths in length, 8 twelfths in breadth; its muscular coat moderately thick, and disposed into two lateral muscles with large tendons; its epithelium, Fig. 2, c d e, thick, hard, with numerous longitudinal and transverse rugæ, and of a dark reddish colour. The duodenum, f g h, curves in the usual manner at the distance of 1 1/4 inch, ascends toward the upper surface of the right lobe of the liver for 1 inch and 10 twelfths, then forms 4 loops, and from above the proventriculus, passes directly backward. The length of the intestine, f g h i, is 16 1/2 inches, its diameter 2 1/4 twelfths, and nearly uniform as far as the rectum, which is 1 1/4 inch long, at first 3 twelfths in diameter, enlarged into an ovate cloaca of great size, Fig. 3. b; the cœca a, a, 41 twelfths long, cylindrical, 1/2 twelfth in diameter, obtuse.