IV ANATIDAE Pia 
politan Family Anatidae, with the Swans, Geese, and Ducks; 
where, in spite of many attempts at subdivision, the lines of 
demarcation cannot yet be finally determined. Count Salvadori, 
however, having lately propounded a carefully-elaborated arrange- 
ment,’ I have adopted his Sub-families in the present volume, 
viz. (1) Merginae, (2) Merganettinae, (3). Erismaturinae, (4) 
Fuligulinae, (5) Anatinae, (6) Chenonettinae, (7) Anserinae, (8) 
Cereopsinae, (9) Plectropterinae, (10) Anseranatinae, and (11) 
Cygninae. 
The skull is short and robust ; while the neck is abnormally 
developed, with extra vertebrae, in the Swans, and is usually 
long, though less so in the Sea-Ducks; in the IMerginae and 
some Fuliqgulinae the customary posterior notches in the sternum 
are converted into two complete fenestrae or apertures. The 
bill is almost entirely covered with a soft sensitive membrane, 
ending in a horny process termed the nail, the skin being warty 
in Anseranas and Chen rossi; Cereopsis has a large tumid cere ; 
both sexes of Cygnus melanocoryphus and C. olor have a knob 
at the base of the culmen, as have the males of Plectropterus, 
Tadorna cornuta, and the domesticated form of Cycnopsis 
cycnoides ; the same sex of Somateria spectabilis has the posterior 
portion of the maxilla spread into a disk; Oedemia has it con- 
siderably swollen even in the female; Cairina and Plectropterus 
have caruncles on the forehead; Sarcidiornis has a fleshy comb 
at the proximal extremity of the beak in the male ; while Biziura 
has a dependent flap on the chin, and a small subgular pouch. 
The bill is usually broad and depressed, and may be sub-conical, 
as in many Geese; spatulate, as in Spatula and Malacorhynchus ; 
or somewhat less dilated, as in Chaulelasmus, and so forth. There 
is a distinct hook at the tip in Mergus, Dendrocycna, and dex ; 
the culmen is contave in Marmaronetta and Stictonetta ; the nail 
is bent inwards in the latter and Lrismatura, while the maxilla 
may overlap the mandible, or the covering membrane may even 
hang over the latter, as in Malacorhynchus, Hymenolaemus, and to 
a less extent in Hlasmonetta and Nesonetta. The length is very vari- 
able, but the thin elongated “ sawbill ” of Mergus, with its serrated 
edges, is especially remarkable. Most characteristic of the Family 
is the presence of highly-developed lamellae or transverse tooth-like 
processes on both maxilla and mandible, which are visible when 
1 Cat. Birds Brit. Mus. xxvii. 1895, pp. 28, 24. 
