THE STEAMER DUCK 
144 
in this connexion. 1 The small diagram of the elbow-joint shows some 
differences from the Mallard, though the qualification added to the 
last sentence should be borne in mind. Thus, it appears from the 
diagram (which the key confirms) that the two tendons of the biceps 
are inserted on the radius and ulna respectively. This is probably the 
commonest arrangement in birds, but in the Mallard one has a double 
insertion on both radius and ulna, while the other is inserted on the 
ulna only. 2 Two small ligaments are figured and labelled, connecting 
the humerus with the ulna (or possibly really with the ulna and radius 
respectively), where in Anas I find a continuous sheet of ligament 
covering the ventral aspect of the elbow-joint and connecting the 
humerus with both bones of the forearm. But apart from such small 
differences and some other minor ones—e. g. in the disposition of the 
ligaments of the wrist-joint—which the diagram appears to indicate, 
the agreement with Anas is very close indeed. So far as can be judged, 
therefore, the peculiar method of progression of the Steamer Duck 
has entailed no significant modification of the ordinary wing 
musculature. 
1 Furbringer ( JJntersuchungen zur Morphologie und Systematic der Vogel, i. 509) 
mentions the Swan ( Cygnus ) as one of the forms in which the ‘division begins already 
in the belly of the muscle’, but no duck. 
2 Haswell ( Proc . Linn. Soc. New South Wales , iv, 1880, 308) quotes the Anatidae 
as an example of birds in which one tendon is inserted on the radius and the other 
on the radius and ulna, but at least in Anas platyrhyncha the condition is as above 
stated. 
