30 R. W. SHUFELDT, 
front of the pars plana, where these two parts are confluent (See 
Fow!’s Skull, tab. 86 figs. 6 and 8, pp. 1—16). But the true remnant 
of the os uncinatum is formed in the intero-external angle of the 
pars plana which is the homologue of the ethmo-palatine of the frog.” 
(„Remnants and Vestiges” in: Proc. Roy. Soc. London, Vol. 43, Febr. 23, 
1888, pp. 400, 401). | 
“Besides the special middle turbinal centre which ossifies nearly 
all the pars plana of these birds, there is formed in the adult a 
small midioline bone in the angle just where the lacrymal ends below. 
There are two such nuclei on the right side, some on the left in 
one of my specimens of the skull of Uria troile, and one the rest of 
my Alcidae, namely, Alca torda and Fratercula arctium. In gulls 
of the first year this angle remains unossified; but in old specimens 
it becomes a distinct os uncinatum, almost as well developed as in 
the albatross. In an old Larus argentatus it is triangular, and the 
lower and longer side which is notched, is two millims. in extent.” 
This is likewise the ossicle I found in Larus argentatus (referred to 
above), and which corresponds exactly with the same ossicle in 
Chloephaga poliocephala, but does not seem to be the ossification I 
have elsewhere described for the Albatrosses.!) This last seems to 
agree with Dr. PArker’s description of theosuncinatum in those 
birds; and in my paper on them in the Proceedings of the U. S. 
National Museum for 1888 I .give quite an extensive notice of it. 
If the true os uncinatum occurs in any ofthe Anatidae, it is 
undoubtedly lost in the average museum specimens of skulls of that 
group, and I have never found it present in any of them. 
When we come to study the osseous structures (and the characters 
they present) to be seen upon a basal view ofthe cranium in 
Dendrocygna (Fig. 53, 54, Pl. 8), the fact is soon appreciated that 
each and any of them practically agree with the corresponding ones 
found in this part of the skull in Anas platyrhynchos, — in fact, 
most of them are identical both in form and relative position, and 
further, they are, in one way or another, different in the skulls of 
other kinds of ducks outside the genus Anas and the larger anserine 
fowls. 
Upon comparing the base of the skull in our specimen of Den- 
drocygna autummalıs (454) with that of a Mallard (A. platyrhymchos. 
1) SHUFELDT, R. W., Observations upon the osteology of the order 
Tubinares and Steganopodes, in: Proc. U. S. nation. Mus., 1888, p. 253—315, 
figs. 1—43. 
