40 R. W. SHUFELDT, 
in ducks and geese, it being practically absent in swans. It is 
individualized and conspicuous in Mergus serrator (see fig. 5, Osteo- 
logy of Birds). 
Among the Anseres, as a rule, the furcula lacks a hypo- 
cleidium, or, if present, it is but a mere rudiment of one (A:x); 
while in some of the geese, as well as in Dendrocygna, we find, on 
the posterior aspect of the arch below, at its middle, a V-shaped 
area, formed by a line on either side, where the externo-posterior 
surface of the furcula terminates. This is also faintly marked in 
Polysticta stelleri; and, while this is likewise the case in Chen hyper- 
boreus nivalis, in the latter the os furcula has the major portion 
of either free clavicular extremity as in Olor, in the matter of form 
as well as in the complete pneumaticity of the bone, — the groups 
of the large pneumatic foramina being on the outer sides, at about 
a centimeter from the sharp-pointed end. 
Harelda hyemalis has a slender and broad U-shaped furcula, 
with its clavicular extremities markedly produced. Both Chenonetta 
jubata and Mergus serrator have the arch still broader and more 
slender; but the free ends of the clavicles are short in the former, 
and long in the merganser, while both possess the process on the 
superior border, small, but very much individualized, and hence a 
conspieuous character (fig. 5 “Osteology of Birds”, and Fig. 67, Pl. 9; 
Fig. 75, Pl. 10 of the present paper). 
Comparative ornithotomists have long known that the three 
bones composing the pectoral arch in birds articulate in differ- 
ent ways with each throughout the Class. These various methods 
of articulation are more or less characteristic of the families and 
the higher groups, and to this the Anseres form no exception.') 
This has been most exhaustively and beautifully demonstrated 
by Max FÜRBRINGER in his magnificent work Untersuchungen 
zur Morphologie und Systematik der Vögel, the second and 
third Plates of the second volume of which presents over one 
hundred figures of the articulations of the bones of the pectoral 
arch in Birds. These beautiful engravings are all lettered, and 
constitute a most instructive series. The Anseres are exampled by 
Mergus, Somateria, Anas, Fuligula, Oygnus, Cereopsis and Unemionus. 
1) See „The Pectoral Arch“ under the article „Skeleton“ in ALFRED 
NEwToN’s A Dictionary of Birds, Pt. 4, p. 856—858, Illus. by Prof. 
Hans GADow. 
