[9]

The Ratitae, Crypturi and Hesperornis have no pygostyle.

[10]

For the best collection of facts, see the various reports of the Migration Committee of the British Association, 1880-1888; and especially that for 1896, containing the Digest of the observations (made at Lighthouses and Lightships) by Mr. W. Eagle Clarke.

[11]

It has been suggested that these flocks of young birds are led by older members of their own species which, though for some cause not breeding, have yet had experience of migration; but of this there is no evidence whatever.

[12]

Cf. W. Dames, Pal. Abhandl. ii. 1884, pp. 119-196; transl. Geol. Mag. 1884, pp. 418-424; Vogt, Ibis, 1880, pp. 434-456; Hurst, Nat. Sci. vi. 1895, pp. 112-122, 180-186, 244-248; Pycraft, op. cit. v. 1894, pp. 350-360, 437-448; viii. 1896, pp. 261-266.

[13]

A doubtful genus, Laopteryx, has been described from the Jurassic by Marsh, Ann. Nat. Hist. (5) vii. 1881, p. 488.