president's address. 15 



Its northern limit on the Atlantic coast is near the thirtieth par- 

 allel. On leaving the Atlantic coast, the northern boundary passes 

 obliquely northwestward, rising in the region of the Chaco Desert, 

 to, or possibly a little beyond, the Tropic of Capricorn. Again, 

 descending to about -the twenty-fifth parallel, it turns abruptly 

 northward and eastward, along the eastern border of the Andean 

 chain, nearly to the fifth degree of south latitude, near which point 

 it strikes the Pacific coast. It thus embraces a large part of the 

 great Andean plateau, with the neighboring coast region to the 

 westward, nearly all the La Plata plains, and the region thence 

 southward to Tierra del Fuego, which belongs also to this region. 



"As contrasted with the Tropical Realm to the northward, it is 

 characterized, in respect to mammals, by the absence of all Quad- 

 rumana and the paucity of Edentates and Marsupials, there being 

 neither Sloths nor Anteaters, while only two or three species of Opos- 

 sums barely extend over its borders ; the absence of all genera of 

 Leaf-nosed bats, and of not less than a dozen important genera of 

 Rodents, the Coatis, the Kinkajou, the Tapirs, and many other 

 genera characteristic of the American tropics.* As noted by Mr. 

 Wallace, it is further characterized by the possession of the entire 

 family of the Chinchillidce, the genera Auchema, Habrocomiis, 

 Spalacopus, Actodon, Ctcnomys, Dolichotis, Myopotamits^ Chlama- 

 dophonts, to which may be added the marine genera Otaria, Arc- 

 tocephahis, Morunga, Lobodon, and Stenorhynchus, very few of which 

 range beyond the northern border of this region. The Spectacled 

 Bear is also confined to it, and here are also most largely developed 

 the Murine genera Calomys, Acodon, and Reithrodon.^'' 



Mr. Allen might have derived additional cogent evidence for the 

 independence of this realm from the fresh-water fishes, which, in 

 fact, show more relationship to those of New Zealand and Tas- 

 mania than to the tropical American types. Indeed, this relation- 

 ship is such that an English rchthyqlogist of some note. Dr. Giin- 



* "Among the genera of the Brazilian region here unrepresented are, aside from 

 the Qttadrnmana, Cercoleptes, Naszia, Tapiriis, Bradypiis, Choelopiis, Alyrmeco- 

 phaga, Tamandua, Cycloi/nirus, Phyllostoma, Glossophaga, Arctibeus, Dysopes, 

 (and other genera of Ckiroptera,) Hydrochccriis, Cercoinys, Daclylomys, Loncheres, 

 Echimys, Ccelogenys, Dasyprocta, Chcetoinys, Cercolabes, Lepics, Sciitnis, Ha- 

 brothriXf Oxymycterus, Holochilus, etc., = 2y-\-.'" 



