THE RED-THROATED DIVER. 305 



Adult Female in summer. 



The female is precisely similar to the male in form and colouring, but is 

 considerably smaller. 



Length to end of tail 25 inches, to end of claws 28 T y, extent of wings 43. 

 Weight 3 lbs. 



Male in winter immature. 



In this state the principal differences are the following: — The fore part of 

 the neck, instead of being of a uniform rich brownish-red, is merely mottled 

 with that colour; all the feathers of the upper surface have each two white 

 spots towards the end; the tail-feathers are edged and terminated with white; 

 the colouring in general is somewhat less pure and deep, and the bill is of a 

 much paler tint. 



Young bird unfledged. 



The young are at first covered with a dense elastic down of a greyish- 

 black colour, tinged with brown. The bill is bluish-black, its basal edges 

 yellow; the iris reddish-brown. 



The width of the mouth is 10 twelfths; but the lower jaw is dilatable to 

 1^ inches. On the palate are two papillate ridges, with two series of papillae 

 on each side of the posterior aperture of the nares, which is oblongo-linear, 

 1-? inches long, and margined with papillae. On the anterior part of the 

 upper mandible are three ridges. The tongue is 1 inch 8 twelfths long, very 

 slender, trigonal, flat above, tapering to a horny point. OZsophagus, a b c, 

 14 inches in length, at its commencement 1^ inches in width, but at the 

 lower part of the neck enlarging to 2 inches; on entering the thorax it 

 contracts to 1^ inches; the proventriculus, b c, again enlarges to 2 inches, 

 forming a very large ovate sac. The lobes of the liver are very large and 

 nearly equal, the length of the one being 3 inches 10 twelfths, that of the 

 other 3 inches 8 twelfths. The stomach, c d ef, is rather large, roundish, 1 

 inch 9 twelfths in diameter, a little compressed, its lateral muscles rather 

 thin, the lower somewhat prominent. Its contents are remains of fishes, and 

 a great quantity of small stones and pebbles. The epithelium is pretty 

 thick, dense, with numerous longitudinal rugae. The proventricular glands 

 form a belt 1 inch 10 twelfths in breadth. The intestine is 4 feet 11 inches 

 long; its average width 8 twelfths. The coeca, Fig. 2, c c, 2^ inches long, A\ 

 twelfths broad, towards the end 6 twelfths, with the extremity rounded. 

 The rectum is 2 inches long, with a globular cloaca, b, 1^ inches in diameter. 



Trachea 111 inches long, much flattened, from 6 twelfths to 4 twelfths in 

 breadth; the rings 145, with 2 dimidiate. Bronchi moderate, of 20 half 

 rings. Lateral muscles strong; a single series of inferior laryngeal muscles 

 going to the last half ring of the trachea. 



Vol. VII. 43 



