ON THE SYSTEMATIC POSITION OF HESPERORNIS. 9 
THE SHOULDER-GIRDLE. 
On the keelless sternum and other characters of the shoulder-girdle of Hesper- 
ornis, Marse lays great stress in his advocacy of the bird’s Ratite affinities. I 
believe that the real affinities here again are obviously with the Colymbide, and 
that the special features are all due to the degenerate condition of the wings. 
In the first place, the sternum shows both in the figure of H. regalis (Marsu, 
Pl. vi., fig. 2), and to a less extent in that of H. crassipes (PI. vii., fig. 3), undoubted 
traces of a rudimentary keel. The oblong, elongated shape, and the two notches in 
the posterior margin, are precisely as in Colymbus, and unlike anything in the Ratitee ; 
and the peculiar articulation with the coracoid, which latter bone fits into a deep 
notch on the ventral face of the sternum, is exactly paralleled in the Colymbide and 
Alecidee. 
The coracoid is remarkably short and broad, much shorter than in Colymbus, 
but its outline, allowing for the shortening up of the shaft, is not dissimilar: in 
particular, we may note the curious angular projection on the outer side of the 
sternal extremity (the epicoracoid of Parker), which is not represented, or very 
feebly indicated, in the Ratites. 
The second point on the strength of which the Ratite affinities have been urged, 
is in the very obtuse angle between the scapula and the coracoid, “the long axis of 
the adjacent parts of the scapula and coracoid being parallel, or identical.” Now it 
is certain that the angle between the coracoid and the scapula is in Hesperornis a — 
very obtuse one, and much more obtuse than in Colymbus or any ordinary Carinate 
bird, though hardly so obtuse as the description above quoted would imply. From 
Marsu’s figure (/oc. cit., p. 58) it would seem to be an angle of about 110°, or very 
nearly the same as in the Emu. But this is a point in which the Ratitee differ very 
considerably among themselves, and I doubt whether it be not a feature too much 
dependent on function to be a safe classificatory guide. But if an apparent Ratite 
affinity be detected here, it is surely more than overthrown by the fact that in 
Hesperornis the scapula and coracoid are separate bones, while in all the known 
Ratites they are united. Not only is this a morphological character of greater 
importance, but it throws some doubt on the accurate measurement of the angle 
itself. 
The clavicles in Hesperornis, though separate, meet in the middle line, and are 
thus better developed than in any Ratite. They resemble in form the clavicles of 
Colymbus, which are much thinned away at their junction, and meet without any 
interclavicular expansion. 
A peculiarity in the proximal extremity of the clavicle in Colymbus, which 
passes beyond the head of the coracoid to articulate by a long tapering extension 
with the scapula, is not found in Hesperornis. 
B 
