Drv Latuam’s Effay on the Trachece 01 Windpipes of Birds. 115 
XIX. ANAS MARILA—Scavr Duck. Tab. xiv. Fig. 3, 4. 
A. nigra, humeris cinereo-undulatis, abdomine fpeculoque alari 
albis. 
Anas Marila, Linn. Syf. Nat. i. p. 196.—Ind. Orn. iis p. 853.— 
Raii Syn. p. 142. A. 6. 
_ Die Bergente, Be/th. der Berl. Nat. Fr. iv. p. 602. t. 17. f. 3, 4. 
Scaup Duck, Gen. Syn. Vi. pe 500.—Br. Zool. it. No. 275. pl. 100. 
—Will, Orn. p. 365. 
The breadth of the /rachea of this fpecies, in the middle, is full 
half an inch ; ‘it leffens a trifle towards the top, but diminifhes very 
confiderably as it approaches the bottom, fo as not to meafure more 
than three lines where it: joins the labyrinthic part's the total length 
is from 73.to 8 inches. We find the name of labyrinth generally 
given to this portion of the windpife of the foregoing Ducks; and 
we continue the appellation, although the correfponding part in 
many may be more aptly compared to a drum, and in courfe the 
word tympanum might be fubftituted for that of ampulla; as this part, 
inftead of being globular, prefents a more or lefs flatted furface, 
covered over with a membrane fimilar to that of'a drum-head, and 
ftretched in the fame manner, This drum-like labyrinth exifts on 
the left fide of the trachea, in refpect to its fituation in the neck of 
the bird, in the fame manner as the globular labyrinths, and in’ the 
Scaup feems to be the moft confpicuous of any that poffefs it. 
The flatted furface of the labyrinth is for the moft part open, ex- 
cept round the rim, and has an irregular bony arch crofling it from 
fide to fide; independent of thefe, the furface is covered with a de- 
licate fine elaftic membrane ftretched over the furface, giving the 
idea of the head of a drum in miniature. The lower part of the 
Q2 bony 
