386 Mr. YARRELL on the Trachee of Birds. 
tent of surface for the insertion of large and powerful pectoral 
muscles; the enlargement at the bottom of the trachea in all of 
them is of bone only. ‘The Wild Duck may be considered the 
type of this division. 
The Eider Duck, King Duck, Velvet Duck, and Scoter, pos- 
sessing some characters common to the preceding class, and 
others belonging to that next in succession, appear to supply the 
link between these two divisions. I regret that the extreme 
rarity of three of the species last named has hitherto prevented 
my obtaining any examination beyond that afforded by the exter- 
nal part of preserved specimens in collections ; and I am there- 
fore unable to state their comparative structure. 
The next division of true Ducks includes in the following or- 
der the Red-crested, the Pochard, Ferruginous, Scaup, Tufted, 
Harlequin, Long-tailed, and Golden Eye; and their general 
distinctions, internal as well as external, compared with those 
of the birds of the first division, will be found of an opposite 
character. Externally they exhibit the neck and wings short, 
the latter only reaching to the origin of the tail-feathers ; the 
tarsi short and compressed; the hind-toe lobated, and an ex- 
tended web to the inner toe. "They frequent the sea, or the 
deep parts of the largest fresh-water lakes, and have been 
called oceanic Ducks; seldom seen on land; their walk em- 
barrassed from the backward position of the legs, but dive 
constantly and with great facility, taking their prey at various 
depths below the surface; their food finned and shell-fish, ma- 
rine insects, but little or no vegetable production; their powers 
of flight moderate. Of their soft parts, the cesophagus is capable 
of great dilatation; the stomach is a muscular gizzard; but 
the internal cavity increases in size, those of the Long-tailed 
Duck and Golden Eye most resembling the stomach of the 
Mergansers ; the intestines and cecal appendages are shorter, 
the 
