In a male bird, the tongue is 10 twelfths of an inch long, sagittate at the base, with conical papillæ, of which the outer are larger, slightly concave above, horny towards the end, which is thin, rather obtuse, and lacerated. On the middle line of the roof of the mouth anteriorly is a row of large blunt papillæ, behind which are two rows; aperture of posterior nares linear. Œsophagus 7 inches long, of moderate width, its greatest diameter, at the lower part of the neck, where it is a little dilated, 8 twelfths. Proventriculus 1-2/12 long; its glandules 1-(1/4)/12 long. Stomach a large and powerful gizzard, broadly elliptical, 1-1/2 inch long, 1-5/12 broad, its lateral muscles large, the tendons covering nearly their whole surface, the left muscles 1/4 inch think, the right 5/12, the cuticular lining moderately rugous. Intestine 21 inches long, from 5/12 to 3/12 in diameter. Rectum 2-3/4 inches; cæca 2, their diameter 3/12 towards the end. Trachea, moderately extended, 5-1/2 inches long, its greatest breadth 3-(1/4)/12, its least 1-(1/2)/12. Its rings 130, very slender, unossified, collapsed, and owing to their narrowness in the middle line before and behind, seeming as if broken there; bronchi with 15 half-rings. The contractor muscles moderate, the sterno-tracheal slender; a pair of muscles on the lower larynx, from the lower rings of the trachea to the membrane over the first bronchial ring. In the mouth was a small frog, in the pharynx two, in the œsophagus two more, a large piece of root, numerous fragments of insects, and a leach, the frogs 2-1/2 inches long. In the gizzard were seeds, and fragments of white fleshy roots. GREAT NORTHERN DIVER OR LOON. _COLYMBUS GLACIALIS_, LINN. PLATE CCCVI. ADULT MALE AND YOUNG MALE.