“Tree-Ducks” of the genus Dendrocygna. 141. 
anteriorly, in which locality there invariably is present an exten- 
sive group of foramina for the capillary supply of the mandibular 
theca. 
This view of the eranium of a Dendrocygna is repeated, in so 
far as its general characteristics go, in many of the ordinary wild 
ducks, among the Anatinae as well as the Fuligulinae, and 
this holds true for species all over the world. It is seen, for ex- 
ample, in the elongated skull of the Canvas-back (Marila valisineria) 
(Pl. 6 Fig. 34); but here the superior orbital peripheries have the 
appearance of having been shaved off, and the group of foramina 
at the distal extremity of the superior mandible are conspicuously 
abundant. 
This upper view of the skull in Dendrocygna autumnalis is, 
character for character, almost identical with what we find in a 
Mallard (Anas platyrhynchos, Pl. 6 Fig. 36), and not so very different 
from what is to be found in such other ducks as Anas rubripes; 
the Teals of the genera Nettion and Querquedula; Spatula clypeata 
and Dafila acuta; the various species of Marila; Chaulelasmus_stre- 
perus;, the Widgeons and, indeed, many other typical ducks. In a 
general way, it agrees with some swans (Pl. 7 Fig. 39); but, in so 
far as I have observed, the fronto-nasal region of the Cygninae, 
on this view of the skull, is always more or less tumerous, very 
conspicuously so in such swans as Cygnus olor (No. 19432, Coll. U. S. 
Nation. Mus.). 
Turning to the skulls of some of the geese and brants, as Anser, 
Chen and Branta, the principal differences seen in these genera 
are: that the cranial vault is higher and more capacious in them, 
and the superior mandible tapers off to more narrow dimensions 
'anteriorly, which is especially well marked in Anser and Chen (Pl. 4 
Fig. 19; Pl. 5 Figs. 24, 25). 
Far greater differences are to be observed when we come to 
compare the superior view of the skull of Dendrocygna with the 
corresponding one in such Anatidae as Chloephaga hybrida, 
‚Cereopsis novae-hollandiae, Tachyeres cinereus (No. 1818, 1819, Coll. 
U. S. Nation. Mus.), and some of the eiders, as Somateria v-nigra 
“No. 7332, Coll. U. S. Nation. Mus.) (Fig. 17, Pl. 4; Fig. 29, Pl. 5, 
and Fig. 35, Pl. 6). In other words, when seen from above, the 
skull of any of these “Tree-Ducks” not only resembles, but actually 
is very much more like the same aspect of the skulls in certain of 
the Anatinae, as the Mallard, Black Duck, the Teals, Gadwall, 
