Migrations of North American Birds. 259 



Celebes^ the IMoluccas, and the Sandwich Islands. Mr. Wallace 

 calls attention to the fact of the very great dissimilarity between 

 the faunae of Bali and Lombok, and of Borneo and Celebes, 

 although geographically very near each other, while islands of 

 the Indian region, as well as of the xlustralian, are respectively 

 very closely allied, although much more remote from each other 

 than those just contrasted. The explanation of this difference 

 he finds in the comparatively slight depth of water between 

 islands of the same region, while the channel separating those 

 of the different regions is almost unfathomable. By an eleva- 

 tion of 50 fathoms, all these islands of one region would almost 

 become joined to the mainland of their respective regions, while 

 the channel separating the latter would still constitute a physical 

 barrier. Hence he infers that subsequent to the original 

 peopling of the Indian and Australian regions, a subsidence into 

 the sea and the consequent production of islands, while it ulti- 

 mately modified the minor characters of the faunae, left the 

 broad outlines unchanged. 



V. North American Region. — Dr. Sclater divides this from 

 the South American somewhere in Mexico, the line reaching 

 further north on the coast, and more to the south in the central 

 mountainous portion. Wallace draws the line about the 

 parallel of 22"^, or near the Tropic of Cancer. To the north it 

 includes Greenland. 



VI. South American Region. — This embraces, accordmg to 

 Sclater and Wallace, the rest of continental America, the West 

 Indies, the Galapagos, the Falklands, &c., while Wallace even 

 includes (very erroneously however) the Sandwich Islands. 



Of the Regions thus sketched out, I propose to confine my- 

 self to the two last mentioned, or those of the New World^ and 

 more especially the portion included in the United States and 

 north of it, and to point out the minor subdivisions and pecu- 

 liarities of the ornithological faunae of the same. Before pro- 

 ceeding, however, to this subject, I may premise that I cannot 

 quite agree with Dr. Sclater in referring the West Indies to the 

 South American Region, but prefer to consider it as having 

 independent rank as — 



VII. West Indian Region. — In winter a large proportion of 



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