He was, indeed, the first to show clearly the relationship of the heron-like birds with the Steganopodes; of storklike birds with the American vultures; the great difference between the latter and the other birds of prey; the connexion of the gulls and auks with the plovers, and that of the sand-grouse with the From Newton's FIG.
A B Y, A Y, A B, X Y and B do not occur at all, some of them for obvious reasons, Occasionally there is an instructive progressive evolution expressed in these formula; for instance Phaethon, in various other respects the lowest of the Steganopodes, has A X Y, Sula and Phalacrocorax have A X, Fregata, the most specialized of these birds, has arrived at the reduced formula A.
In the Steganopodes they tend to become much reduced, e.g.
Steganopodes.- Well flying, aquatic, nidicolous; with all the four toes webbed together.
Cormorant (q.v.) and gannet as well as the true pelicans, and for a long while these and some other distinct groups, as the snake-birds (q.v.), frigate-birds (q.v.) and tropic-birds (q.v.), which have all the four toes of the foot connected by a web, were regarded as forming a single family, Pelecanidae; but this name has now been restricted to the pelicans only, though all are still usually associated in the suborder Steganopodes of Ciconiiform birds.
Orders: Ichthyornes, Colymbiformes, Sphenisciformes, Procellariiformes, Ciconiiformes, (Suborders: Steganopodes, Ardeae, Ciconiae, Phoenicopteri), Anseriformes (Sub-orders: Palamedeae, Anseres), Falconiformes (Sub-orders: Cathartae, 1 Craniata may be usefully divided into 3 grades: (a) Branchiata Heterodactyla, which includes Pisces except Cyclostomes.