SCLATEE ON TIIE OENERAL DISTRIBUTION OF AVES. 143 



mentioned the chief genera common to the northern portions of 

 both hemispheres. These are also characteristic of Nearctic in 

 contrast to Neotropical zoology, as none of them extend into 

 Southern America. The ornithology of the U. S. of America 

 (which now embrace a very large proportion of the Nearctic 

 region) contains upwards of G20 species. 



Calculating the area of the Nearctic Eegion at six millions and 

 a half of square miles, and the species peculiar to it at 660, we 

 have aboiit 9000 miles for each species, making this region, as 

 might have been supposed, the least productive of ornithic life, 

 after the Palaearctic. 



VI. Neotropical or South-American Eegion {Begio Neo- 

 tropica) . 



Extent. — "West India Islands, Southern Mexico, Central Ame- 

 rica and whole of S. America, Galapagos Islands, Falkland Islands. 

 Estimated area of about 5,500,000 square miles. 



Characteristic forms. — 1. (Continental.^ Sarcorhamphus, Ibycter, 

 Milvago, Thrasaetus, Cymindis, Herpetotlwres, Steatomis, Nycti- 

 bius, Hydropsalis, Eleothrepttcs, Trogon, Bucco, Monasa, Galbula, 

 Furnarius, Synallaxis, Anabates, Oxyrhamphus, Dendrocolaptes, 

 Pteroptochos, BhampJwccenus, Campylorhynclms, Hylophihis, Les- 

 sonia, Agriomis, Formicarius, Formicivora, GraUaria, Tcenioptera, 

 Tityra, Conopophaga, Fipra, Btipicola, Phceniccrcus, Cotinga, 

 Gymnoderus, Cephalopterus, Vireolanius, Cyclorhis, Thamnophilus, 

 Tanagra, Calliste, Saltator, Fuphonia, CatamblyrJiynchus, Fkyto- 

 toma, Opistlwcomus, Ramphastos, Picumnus, Geleus, Crotophaga, 

 Caltrides, Penelope, Oreopliasis, Crax, Thinocorus, Tinamus, 

 Psvphia, Gariama, Furypyga, Parra, Palamedea, Ghauna, Aramns, 

 3ferganetta, Heliornis. 



2. (Antilles.) Todus, Priotehis, Ginclocerthia, Dulus, Loxigilla, 

 Phcenicopliihis, Spindalis, Glossiptila, Teretristis, Saurothera. 



3. (Galapagos.) Certhidea, Cactornis, Camarhynchus, Geospiza. 



There can be no question, I think, that South America is the 

 most peculiar of all the primary regions in the globe as to its 

 ornithology. There are at least eight or nine distinct families of 

 birds which are quite confined to this country, many of these em- 

 bracing a multitude of different genera and species. The TrocJii- 

 lidce (which are the distinguishing family of the new world par 

 ciiipliase) are now known to be more than 320 in number, and 



