The Holarctic Region 31 



Regions and the present, there is a certain alliance, as was long ago suggested by 

 Professor Huxley, though of quite a different nature from any thus far con- 

 sidered. "South America, that is to say the most important part of the Neo- 

 tropical Region, retains a greater proportion of the less modified descendants of 

 generalized ornithic types than does any other portion of the globe, the two 

 Regions before mentioned only excepted." NEWTON. In other words, this area 

 appears to have been more or less completely isolated for a very long period of 

 time, and as a result a large proportion of the archaic elements have been re- 

 tained, albeit in modified form. Among the birds, then, we find a large number 

 of peculiar types, including the orders Rheiformes (Rheas) and Crypluriformes 

 (Tinamous), and some twenty-seven families or subfamilies, as follows : Procnia- 

 tid(E (Swallow-Tanagers), Ccerebida (Honey-Creepers), Zeledoniida (Wren- 

 Thrushes), CatamblyrhynchidcB (Plush-capped Finches), Ptilogonatidce (Silky 

 Flycatchers), Dulida (Palm Chats), Oxyruncidte (Sharp-bills), Piprida 

 (Manakins), Cotingida (Cotingas), Phytotomida (Plant-cutters), Dendrocolap- 

 tidce (Wood-Hewers), Formicariida (Ant-birds), Pteroptochida (Tapacolas), 

 Rhamphastidce (Toucans), Bucconida (Puff-birds), Galbulida (Jacamars), 

 Todida (Todies), Momotidce (Motmots), Steatornithida (Oil-birds), Cracida 

 (Curassows), O pisthocomida (Hoactzin), Chionidce (Sheath-bills), Thinoco- 

 rida (Seed-snipe), Cariamida (Cariamas), Aramida (Courlans), Psophiida 

 (Trumpeters), Eurypygidce (Sun-bitterns), Palamedeidce (Screamers). 



In addition to the above-mentioned peculiar forms the following families are 

 mainly Neotropical, only relatively few species crossing the line into the Hoi- 

 arctic Region: Icterida (Troupials), Tanagrida (Tanagers), Tyrannida (Tyrant- 

 birds), and TrochilidcB (Hummingbirds). 



The Holarctic Region. Notwithstanding the fact that this vast Region is, 

 area for area, much larger than all the others combined, it is the most difficult 

 to satisfactorily define. Even the outlines are still open to question in many 

 places, and can be given only approximately. In the New World the southern 

 line of the Holarctic Region has been worked out with considerable detail, being 

 in fact the northern line of the tropics. Starting on the Pacific coast, it crosses 

 the lower portion of the peninsula of Lower California, thence crossing to the 

 Mexican mainland it skirts the mountains and passes over into the Atlantic 

 drainage in southern Mexico, when it bends northward to leave the continent in 

 extreme southern Texas just above the mouth of the Rio Grande. Crossing the 

 Gulf of Mexico, it excludes a portion of southern Florida and the Bermudas and 

 touches the z\frican coast about the vicinity of Mogador, where its course is clear, 

 for it follows the northern limit of the Great Desert. As regards its extension 

 across the Asiatic continent to the Pacific we may accept the recent statement of 

 Mr. H. E. Dresser, who supposes it to "run to the northward of the Arabian 

 Desert, and including the tableland of Persia, the highlands of Baluchistan, the 

 whole of Afghanistan, and the Himalayan Range above about 6000 feet, stretch- 

 ing to the south of Tibet, and north of the valley of Yang-tse-kiang as far as the 

 Pacific, and then around Corea, and the main islands of Japan." 



The Holarctic Region may be divided into two major areas (denominated 



