“Tree-Ducks” of the genus Dendrocygna. 13 
and vertically elliptical; while the occipital crest nearly meets in 
the median line above, being separated there by only 2,5 mm. One 
of the remarkable features of the skull of this species is the extreme 
shallowness, and the almost entire lack of definition of the crota- 
phyte fossae. It may be noted here that the superior mandible of 
this interesting form is conspicuously short as compared with the 
rest of the length of the skull. Presumably, this is ‚likewise the 
case with the lower mandible; but for that I cannot vouch, as it is 
missing from the incomplete skeleton at hand (No. 19213, Coll. U. S. 
Nation. Mus.) (see Pl. 10). 
In Anser and Cereopsis, especially in the latter, most of the 
characters to be seen on the posterior aspect of the skull are but 
feebly pronounced. With respect to Cereopsis novae-hollandiae, the 
hinder part of the cranium is considerably rounded, in conformity 
with the lateral and superior regions, thus subordinating all sharp- 
ness of definition. This famous goose has the crotaphyte fossae 
almost eliminated; the supraoccipital prominence scarcely at all 
defined; the lateral foramina minute, and the occipital crest low 
and thin (Fig. 11, Pl. 3; Fig. 17, Pl. 4). 
In Hymenolaemus malacorhynchus the foramen magnum is of great 
size; the crotaphyte fossae unusually spacious below; the condyle 
extremely small, and the paroccipital processes broad, thin and 
platelike. 
Passing next to a comparative study of the characters to be 
found upon a lateral view of the skull of Dendrocygna autumalis (454) 
with the corresponding ones in various species of Ducks, Geese and 
Swans, we again note the general resemblance of the skull of the 
Tree-Duck to that of a Mallard (Anas platyrhynchos), or to several 
other species of that genus. (Fig. 12, Pl.3; Fig. 38, Pl. 6; compare 
also with Fig. 27 of Pl. 5 and Fig. 32 of PI. 6). 
Nearly allAnatidae exhibit an unusual enlargement or develop- 
ment of the lacrymal bone. In fact, at the present writing, I 
can recall but a single exception to this rule, and I refer to 
Ohenonetta jubata of Australia. In that peculiar little species, the 
descending process of the lacrymal is slender and small, with its 
extremity but very moderately expanded. In most anatine fowls, 
this apophysis is not only greatly elongated, flattened from side to 
side, and expanded at its backward-extending extremity, but makes 
an extensive articulation with the frontal of the same side, and 
posteriorly is often produced backwards, upwards and outwards as 
