218 MERGANSER SERRATOR. 



intestine is five feet long, from five-twelfths to three-twelfths 

 in width. The coeca are oblong, an inch and a half in length. 

 The rectum is five and a half inches in length, its cloacal 

 dilatation an inch and three-fourths in width. 



The trachea, which is about eleven inches in length, when 

 moderately extended, is at first, for two inches and a quarter, 

 nearly four-twelfths in width, but then expands into an oblong 

 dilatation three inches long, and ten-twelfths in breadth, after 

 which it contracts to less than three-twelfths, enlarges a little 

 to nearly four-twelfths and a half, and so continues to the 

 tympanum. The number of rings is an hundred and fifty, of 

 which twenty-eight at the lower part are very broad behind, 

 and very narrow before. The form of the enormous dilata- 

 tion diflfers from that of the Merganser. Several of the lower 

 rings unite and become enlarged, passing nearly in the 

 median line ; but there are two tympaniform expansions, one 

 on the right side, with two membranes, another on the left 

 with one large membrane. The bronchi, short and wide, 

 with twenty half-rings, come off at the distance of ten-twelfths 

 from each other, the right longer than the left. The greatest 

 length of the tympanum is two inches, the gi-eatest breadth 

 an inch and a half. 



The nostrils are oblong, two-twelfths and a half in length, 

 sub-basal, lateral, pervious. The eyes small, two-twelfths 

 and a half in breadth. The aperture of the ear scarcely one- 

 twelfth across. The feet, which are short and strong, are 

 placed far behind. The tibia is bare for a quarter of an inch. 

 The tarsus very short, much compressed, anteriorly with a 

 series of twenty-five rather small, narrow scutella, and about 

 twelve external, the sides reticulated with small flat scales. 

 The first toe is very small, elevated, arched, with twelve 

 scutella, and a lobiform membrane ; the second toe about half 

 an inch shorter than the third, with thirty-five oblique scu- 

 tella ; the third forty-two ; the fourth of about the same 

 length, with forty-six scutella ; the second toe Avith a two- 

 lobed membrane, the outer with a thick margin ; the interdi- 

 gital membranes reticulated, with concave margins. The 

 hind claw very small, curved, compressed, the rest small, 

 compressed, convex, obtuse, that of the tliird toe depressed. 



