“Tree-Ducks” of the genus Dendrocygna. 27 
correspondingly concaved from side to side below. The usual facets 
are found at its anterior and posterior ends; and, mesially, just 
anterior to the latter, we find a perfectly circular foramen, having 
a diameter of about two millimeters. This glosso-hyal foramen 
I have not previously described, and it is possible that it may be 
found in the same bone in the tongues of other scoters, or, perhaps, 
other ducks related to them. 
In this Surf Scoter the first basibranchial is short, rather broad, 
and markedly compressed from above, downward, — a compression 
which causes the articular facet at its anterior end to appear unusu- 
ally prominent. The thyrohyal elements are much the same 
as we find them in other ducks, or as they have been described 
above (No. 81712, Coll. U. S. Nation. Mus.). 
I have given no especial attention to the comparative morpho- 
logy in the Anseres, and have examined the circlet of selerotal 
plates, as found in the eye, in only a few species. There is a 
general description of this last and one for O. perspieillata in my 
Osteology of Birds (p. 282). They have the general characters as 
we find them in the group Dendrocygna, and within the group have 
but very slight value in the matter of determining relationships. 
Osteology of the Respiratory and Vocal Organs. 
Notwithstanding the fact that they are mere sketches, some of 
the best illustrations extant of the ossifications, which occur in the 
vocal organs and the respiratory apparatus generally of the An- 
seres, are to be found in T. C. Eyrow’s „Supplement“ to his 
Osteologia Avium. 
These are, as a rule, life size, and present very fair represen- 
tations of these structures as they occur in Oygnus, Alopochen aegyp- 
tiacus, Querquedula erecca, Anas platyrhynchos, Nyroca lewcophthalmus, 
Harelda. glacialis, Olangula clangula, Mergus serrator, Chloephaga ma- 
“gellanica, Carina moschata, Tadorna belloni (tadorna?), Arctonetta 
fischeri, Aix sponsa; and others known to him as Querquedula for- 
mosa, Oyanopterus cürcia, Micropterus patachonichus, and Bernicla ant- 
arctica. 
Often there is a remarkable difference in the morphology of 
these parts, in so far as they ossify in the two sexes of the same 
species. In some species, the male may have the lower larynx very 
elaborately developed and ossified, while the female of the same 
