OF MICROPTERUS CINEREUS. 499 
coracoid articulation, and about eight lines from the costal region, a vacuity of con- 
siderable size, apparently the result of deficient ossification. ‘The furcula is compara- 
tively feeble, being thinner and less massive than in the Muscovy and many other 
Ducks. The process at the junction of the rami is either entirely absent or very 
slightly developed. The scapula and coracoid do not present any striking peculiarities. 
Bones of the wing. The differences existing between the bones of the wing of the 
Steamer and Muscovy Duck, in respect of general form, are not of great importance. 
The shafts of the humerus and ulna are stouter in the latter bird. The depressions 
marking the origin and insertion of the brachialis internus are larger and deeper, how- 
ever, in the former. The metacarpal differs very slightly, as regards form, from the 
corresponding bone in other Ducks. The second phalangeal joint of the first finger and 
the third of the second are well developed, though from their minute size they are very 
easily lost in the process of maceration. Indeed, although they are probably present in 
all the species of Anatidz, they are almost invariably absent from their skeletons as 
exhibited in Museums. 
Pelwic girdle. The two halves, 7.e. the united ilium, ischium, and pubis, are only 
united synchondrosially to the sacrum in flying birds. The ischiadic foramen is of 
considerable size, being larger than in the Mallard and Muscovy, but smaller than in 
Biziura lobata. The posterior extremity of the pubis is dilated in male specimens. 
Bones of the leg do not, so far as my examination goes, exhibit any very marked 
peculiarities. The ecto- and pro-cnemial processes of the tibia are well developed; and 
the metatarsus tapers in a greater degree from either extremity towards the middle 
than in the other Ducks examined by me. 
DESCRIPTION OF THE PLATES. 
PLATE LVIII. 
Fig. 1. Tongue, natural size, upper surface: a, rima glottidis. 
Fig. 2. Lower part of trachea, lower larynx, and bronchi of adult male Micropterus : 
a, trachea; 6, sterno-tracheal muscles; c, lower larynx; d, bronchi. 
Fig. 3. Ditto of male Chloephaga magelianica, for comparison. Lettering the same. 
The lower larynx, as will be observed, is much more capacious; but its walls 
are much thinner than in the Micropterus, readily yielding to pressure by 
the finger. 
Fig. 4. Stomach of Micropterus, from the side, natural size: @, musculus intermedius ; 
bb, musculi laterales or digastrici. 
Fig. 5, Antero-posterior vertical section of ditto: a, musculus intermedius; 4, musculi 
laterales ; ¢, internal coat of gizzard. 
