510 MB. O. SALVIN ON THE GALAPAGOS AVIFAUNA. 



''Stria- and Asio, Zenaida, Larus, and Spheniscus. Then those of Bendroeca, Progne, 

 Buforides, Nycticorax and Porzana, and, finally, Bolichonyx orizivora, Ardea herodias, 

 and the Ducks, Flamingo, Gannets, Plovers, and Sandpipers, though of these last a 

 constant stream of immigrants may have been maintained from the earliest times. It 

 must be remembered, however, that no precise order of immigration can be absolutely 

 laid down, even approximately ; for one term in the proposition is an absolutely unknown 

 quantity. We know nothing of the rate of change that has taken place in any one 

 species. Outward circumstances may have acted upon one species so as to leave it little 

 changed in a given time, whilst in the same time another species may have assumed 

 distinctive generic characters. Viewing the very peculiar physical characters possessed 

 by these islands when contrasted with the neighbouring American shores, it would seem 

 reasonable to consider that the rate of change demanded of an immigrant species would 

 be high ; consequently the origin of the islands need not be dated back to a more 

 distant period than seems indicated by their volcanic origin. But I am writing of the 

 Birds alone; other forms of life found in these islands present far more complex 

 problems for solution, into which I am not prepared to enter. 



DESCRIPTION OF THE PLATES. 



PLATE LXXXIV. 



Outline Chart of the Galapagos Islands, taken from the Admiralty Chart, No. 1375. 



The dotted line shows Dr. Habel's route. 



PLATE LXXXV. 



Camarhynchus variegatus, p. 489 : fig. 1, c? ; fig. 2, ? . 



PLATE LXXXVI. 



Camarhynchus habeli, p. 490 : fig. 1, <S ; fig. 2, $ . 



PLATE LXXXVII. 



Larus fuliginosus, p. 505: fig. 1, adult; fig. 2, immature. 



PLATE LXXXVIII. 

 Figs. 1 & 3. (Estrelata phmopygia, p. 507. Fig. 2. Procellaria tethys, 507. 



PLATE LXXXIX. 



Spheniscus mendiculus, p. 508. 



All the figures are taken from specimens in the collection of Mr. Godman and 

 myself, except those of (Estrelata phceopygia and Procellaria tethys, the originals of 

 which are in the British Museum. 



