OEDEK IV. 



RASORES. 



Ch. — Bill not longer than the head ; the terminal portion more or less vaulted, hard, with or without a soft skin intervening 

 between it and the head. Nostril with an overlapping fleshy or leathery scale or valve extending over its upper edge. 



In the table on page 2 of the present report I have given a synoptical view of such orders 

 as belong to the United States, borrowed chiefly from Keyserling and Blasius. This, however, 

 will be found to contain several important errors, especially in reference to the position of the 

 hind toe. This is stated to be raised above the level of the rest in Basores, Orallatores, and 

 Natatores, and such is generally the case ; but in the Golumhae and Penelopidae, of the first 

 order, and the Ardeadae, of the second, it is inserted either nearly or quite opposite the others. 

 This is only one of the many illustrations of the difficulty of expressing the characters of the 

 primary groups in ornithology by a single concise phrase, the transition from one to the other 

 being so gradual as to render it almost impossible to say where one ends and another begins. 



In the table just referred to, and in the arrangement and succession of the higher divisions 

 of the volume, I have not pretended to follow the more recent ideas of Bonaparte and others. 

 My object was merely to indicate the North American species of birds, especially those collected 

 by the government expeditions, with their range and distribution, and not to attempt any of the 

 higher generalizations. For this reason I have followed the older division into orders, although 

 that of Bonaparte in many respects is more philosophical. This author arranges birds into two 

 sub-classes, called AUrices and Praecoces, accordingly as their young require to be brought up in 

 the nest, or are able to run about immediately after birth and gather food for themselves. 



Each of these sub-classes is divided into orders^ which range in parallel series, as shown in 

 the accompanying table, taken from volume XXXVII of Comptes Eendus, for October 31, 1853. 

 It will be seen from the table that the Inepti (dodo, &c.,) of the AUrices represent the Stru- 

 thiones (ostriches) of the Praecoces; the Gyrantes, or true doves, the gallinaceous birds ; the 

 Herodiones, or herons, &c., the Grallae (sandpipers, snipes, &c.); the Gaviae, or gulls, pelicans, 

 &c., the Anseres, (ducks, grebes, penguins, &c.) The parallelism in this case corresponds, to a 

 certain degree, with that which prevails in the mammals between the Marsupiata and the 

 Placentalia, and the time will probably come when naturalists will as little think of mixing up 

 the AUrices and Praecoces in the same order, as they now do a similar combination of the 

 marsupial and non-marsupial mammals. 



The position of the hind toe seems to have a direct relationship to the mode of life of the 

 bird. Those species which live on or among trees, and especially which nest and bring up their 

 young there, have the hind toe elongated, and placed low down more or less on a level. with the 

 anterior ones, apparently to facilitate prehension. Such we see to be the case in the herons, and 

 a few other arboricole waders, and in the Penelopidae and Megapodidae of the gallinaceous 

 birds. Some of the doves exhibit a tendency to an elevation of the hind toe ; this, at any rate, 

 appears to be the case in Starnoenas. 

 July It 1858. 



75 b 



