4 
114 Dr. Larwam’s Bify on the Tracheee or Windpipes of Birds. 
a trifle fmaller cowards the bottom: the bony arch, as in others, 
finifhes thé bottom part, and feems as if furnifhed with rings, but, 
they are not moveable as in the reft of the trachea. The orbicular 
labyrinth is attached to the fide of it; this is not fmooth on the 
furface as in the Pintail and Wigeon, but univerfally rough, and irre- 
gularly furrowed with ‘fine indented lines. The oppofite fide runs 
into a pear fhape, and is placed obliquely, with the pointed end 
loweft, as in the two laft named birds, but is flatted confiderably on 
the furface. The bony arch on this fide is fmooth, having no ap- 
pearance of rings, and is bent at a fmall angle from the trachea, 
although it conftitutes a continuance of it: this is the defcription of 
the organ in a young bird. 
In a fpecimen fomewhat more advanced in age, with which I 
was favoured by Mr. Lamb of Reading, the bony labyrinth ap- 
proaches more to a rounded fhape, and is larger, but ftill retains the 
rough furface, and the appearance of bony rings on the arch feems 
lefs diftiné&t ;—and in anold bird, the drawing of which! was favoured 
with by Mr. Boys, the labyrinth is not only much larger in fize, but 
is nearly globular, and the bony arch quite fmooth : yet Mr. Boys 
obferves, that the labyrinthic part is finely granulated and faintly 
wrinkled, and the texture firm and bony; but in this laft circum- 
{tance it does not differ from the younger ones. As to that figured 
by Dr. Bloch, in the Berlin Tranfaétions, it feems at firft fight too 
large by many degrees; yet I will not venture tofay that his figure of 
it is faulty, for in cafe the Mufcovy Ducks ever arrive at twice the 
fize we ufually fee them in England, which they are faid to do in 
warm climates, no doubt but the labyrinth will bear its due pro- 
portion. 
XIX. ANAS 
