The Charadriiformes are here taken to consist of five Sub-Orders. Of these the LIMICOLAE contains the Families _Charadriidae_ (Plovers, Sandpipers, Snipes, and so forth), _Chionididae_ (Sheath-bills), _Glareolidae_ (Pratincoles, Coursers, and Crab-Plover), _Thinocorythidae_ (Seed-Snipes), _Oedicnemidae_ (Stone-Curlews), and _Parridae_ (Jaçanas); the LARI possesses one Family, _Laridae_ (Gulls, Terns, and Skuas); the ALCAE only the _Alcidae_ (Auks); the PTEROCLES, the _Pteroclidae_ (Sand-Grouse); but the COLUMBAE may be divided into _Dididae_, _Didunculidae_, and _Columbidae_. The first three may again be combined into a Laro-Limicoline group, and the last two into a Pteroclo-Columbine, in accordance with their affinities. In structure the LIMICOLAE are sufficiently uniform to be considered simultaneously. The bill furnishes a useful means of subdividing the _Charadriidae_. It is hardest in _Haematopus_, _Ibidorhynchus_, _Strepsilas_, and so forth, being in them bony throughout. In _Charadrius_, _Aegialitis_, _Lobivanellus_, _Vanellus_, and the like, it has a hard tip, but is comparatively flexible towards the base. These may compose Sub-family (1) _Charadriinae_. In _Totanus_, and its nearest allies, it is still hard at the tip, but more flexible at the base. In _Tringa_, and similar genera, it ceases to be hard at the tip, and is slightly endowed with nerves. These may constitute Subfamily (2) _Tringinae_. In _Scolopax_, _Gallinago_, and _Rhynchaea_ it becomes highly nervous at the tip, and therein differs from that of all other birds. These form Sub-family (3) _Scolopacinae_. In _Himantopus_ and _Recurvirostra_ the bill is so attenuated as hardly to be called hard at the tip, but it has no nerves there. The form of the beak varies greatly, being asymmetrical and twisted to the right in _Anarhynchus_, up-curved from the middle in _Avocetta_, wedge-like in _Haematopus_, much flattened in _Tringa platyrhyncha_, spade-shaped in _Eurynorhynchus_, arched in _Numenius_, and strongly decurved in _Ibidorhynchus_. In the Chionididae a horny sheath covers the base of the maxilla, and is indicated by faint lines in the young; in _Glareola_ the bill is short, curved, and very {269}deeply split, making a wide gape; in _Dromas_ it is hard, deep, and compressed; in _Cursorius_ thick and little bent; in the Thinocorythidae Fowl-like; in the Oedicnemidae short, stout, and blunt; in the Parridae narrow and pointed, with a skinny frontal plate, and occasionally with rictal wattles. The nasal grooves are very long in _Ibidorhynchus_, _Totanus_, _Scolopax_ and elsewhere.