SCAPTOCHIRUS.. ANUROSOREX.. Urotrichus. Sorex CRO:EOPUS Crocidura. CRICETUS CRICETULUS. RHOMBOMYS.. PSAMMOMYS. SMINTHUS Arvicola Evotomys MYOSPALAX. ELLOBIUS SIPHNEUS SPALAX. Dipus.. ALACTAGA Sciurus Tamias Sciuropterus Hystrix... Lagomys. Lepus. + + 1 + + 1 + + + +1 +1 +1 +1 +1 +++ 1 1 1 1 ++11 ++1 +1 1 ++++++ +++++++i+i+ili+ + + +++1+I +1+11 ++ 11+1‡++ !++ 1 ¦ ¦ ¦ ++++++ i +++++++++++ 1 1+1 1 1 ++++11 11 +++ +++ 1 ++++++++++++ Summary. + 1 1 1 + + +1 +1 1+1 1+1 | | +1 +1 1 + + + + + + 1 + ÷ +11 ++ +++++1 +1 1 1 1 1 ++++++i+1 1+1+ Whole number of genera Peculiar to the region Circumpolar Of general distribution throughout the region.. Occurring in the Cold Temperate Subregion Occurring in the Warm Temperate Subregion. Genera occurring in the Western Temperate (European) Province. 107 36 22 15 54 80 48 Genera occurring in the Eastern Temperate (Asiatic) Province.. Genera common to the Eastern and Western Temperate Province... Maritime genera common to both European and Asiatic coasts 46 60 65 38 50 6 3 In comparing the North American Region with the Europæo-Asiatic Region, the following resemblances and differences become apparent:-1. The number of genera in the Europæo-Asiatic Region is rather more than one-fourth greater than in the North American Region, with consequently a smaller proportion of circumpolar genera. 2. But this difference results almost wholly from the greater preponderance of peculiar types in the Southern Subregion, due evidently to the immensely greater extent and greater physical diversity of this portion of the EuropæoAsiatic Region as compared with the corresponding portion of the North American Region. 3. While the colder portions of the two regions have each about the same number of genera, which are in great part (nearly two-thirds) common to the two regions, the Warm Temperate (really Subtropical) Subregion of the Europæo-Asiatic Region has a far greater number of genera that do not extend to the northward of it than has the Warm Temperate Subregion of the North American Region, while a small proportion only (chiefly arctopolitan and subtropicopolitan) are common to the two subregions. Hence, 4. The two regions (Europæo-Asiatic and North American) are mainly differentiated (as already noticed) through the presence of genera limited to their southern subregions. III.-AMERICAN TROPICAL REALM. The American Tropical Realm is approximately bounded by the northern and southern mean annuals of 70° F. Its northern boundary has been already indicated in defining the southern limit of the North Temperate Realm, it being concurrent with the southern boundary of the North American Temperate Region. The southern boundary of the American Tropical Realm leaves the Atlantic coast near the thirtieth degree of south latitude, or near the southern extremity of Brazil, but in passing from the coast sweeps rapidly northward till it nearly or quite reaches the Tropic of Capricorn in Northeastern Buenos Ayres; it then bends to the southward and continues westward to the eastern base of the Andes. The Andean chain forms its western limit thence northward to Ecuador, where it crosses the Andean highlands and is again deflected southward, thus including a narrow belt of the coast region west of the Andes in Northwestern Peru. As thus defined, the southern border of the American Tropical Realm is nearly coincident with the southern boundary of the "Brazilian Region" as mapped by Mr. Wallace,* Brazil, nearly all of Paraguay, and Bolivia east of the Andes being included within this realm. Its characteristic genera include all of the American Quadrumanes (families Cebidæ and Mididæ,=Hapalidæ of most authors), all the American Edentates, and nine-tenths of the American Marsupials. It is also the home of nearly all the American Felida, except the Lynxes. It also has many peculiar genera of Glires and Chiroptera, while it almost altogether lacks the characteristic forms of mammalian life found in the northern temperate regions. Among the characteristic North American types unrepresented in the American Tropical Realm are, among Carnivores, not only the Lynxes, but the true Wolves and Foxes, the Martens, Wolverenes, Badgers, and Bears; among Ungulates, the Pronghorn, the Bison, Mountain Sheep, and Mountain Goat, and several important genera of the Cervidae; among Rodents, the Spermophiles, Marmots, Muskrat, Beaver, Pouched Rats, "Gophers" (Geomys and Thomomys), the numerous species of Arvicola, etc.,-in short almost all of the prominent and characteristic genera of the order except the almost cosmopolitan genera Lepus and Sciurus; among Insectivores, all the Moles and Shrews, except a few forms of the latter, which extend over most of the Central American Region. The American Tropical Realm is divisible into three regions,—the Antillean, the Central American, and the Brazilian. The Antillean Region includes only the West Indies and the southern extremity of Florida. The Central American Region embraces Mexico (exclusive of the elevated tablelands), the whole of Central America, and the extreme northern parts of South America (Venezuela north of the Orinoco Basin, Northern and Western New Granada, and most or all of that portion of Ecuador west of the Andes). The Brazilian Region comprises all the intertropical parts of South America not embraced in the Central American Region, including the whole area east of the Andes southward to the boundary already given. Central American Region.-Of the genera occurring in the Central American Region (see subjoined table), only about one-ninth can be considered as peculiar to the region; about one-sixth are either subcosmopolitan or tropicopolitan; about three-fifths range also over the Brazilian Region, and a few over nearly all of South America; about onehalf extend far into North America, among which are several that are also common to the greater part of the North Temperate Realm, while about one-eleventh are also found over most of both North America and South America. Aside from the few peculiar genera, the fauna is composed largely of genera common also to the Brazilian Region, which find their northern limit of distribution within the Central American Region, plus a very large proportion that extend southward from the North American Temperate Region, and which find their southern limit of distribution within the region under consideration. Its distinctive * Geogr. Dist. Anim., vol. ii, map facing page 3. Bull. iv. No. 2- -3 feature is hence an approximately equal blending of temperate and tropical forms, whose respective habitats here overlap. Many of the northern forms do not quite reach the southern limit of the region, just as many of the southern forms do not quite reach its northern limit. It is distinguished from the North American Temperate Region by the preponderance of tropical life, and from the Brazilian Region by the copious intermingling therewith of northern forms, an element wholly lacking in the Brazilian Region. Peculiar or mainly limited to the region Occurring also over most of the Brazilian Region.. Occurring also over much of the North American Region.... Occurring also over most of both North and South America, but not in the Old Subcosmopolitan 63 6 40 .24 5 8 2 Antillean Region.-The Antillean Region differs from both the Central American and Brazilian most strongly in negative charactersthrough what it lacks rather than in what it has-although it possesses a number of peculiar genera. The Chiroptera form two-thirds of the genera and not less than five-sixths of the species. Of the eight peculiar genera, five are Bats, the others being Solenodon (the only In. sectivore), Capromys, and the closely allied Plagiodonta, which together constitute a family peculiar to the region. Two orders-Primates and Bruta-highly characteristic of the Central American and Brazilian regions, are wholly absent. There are also no Ungulates, very few Carnivores, and very few Rodents; the latter, however, are of mostly peculiar species, as are many of the Bats. The single Insectivore is of a remarkable type, which finds its nearest ally in the remote island of Madagascar, the ordinary Insectivores of the neighboring Central American and North American Regions being wholly unrepresented. Genera of the Antillean Region. Brazilian Region.-Of about ninety commonly recognized genera, a little less than one-third may be considered as either wholly or mainly restricted to the region; a little less than another third range to the northward over much of the Central American Region, and may be considered as characteristic of the American Tropical Realm at large rather than of the Brazilian Region. About one-tenth of the remaining genera occur also over a large part of the Central American Region, while the remainder are divided about equally between tropicopolitan and cosmopolitan genera, and those that range southward over the South American Temperate Realm. One genus is also East Indian and another African, while quite a number range throughout the temperate and tropical parts of both Americas, and a few others over Temperate South America. It is eminently characterized by its dozen genera of Monkeys, which, excepting a few that range into the Central American Region, are restricted wholly to this region; also by twelve to fifteen genera of Bats, which are scarcely found beyond its borders; nearly as many genera of Rodents, and quite a number of peculiar genera of other groups. Negatively it is characterized by the absence of Insectivores, the great bulk of the northern types of Carnivores, Ungulates, and Rodents. Its sole affinity with the life of the North Temperate Realm consists in the presence of a few such wide-ranging (cosmopolitan) genera as Felis, Sciurus, Lepus, Vespertilio, etc., and two other genera (Procyon and Didelphys) that range far into North America. It is susceptible of division into several provinces, upon the detailed * Dr. Coues gives Hesperomys (Oryzomys) palustris as Jamaican.-Mon. N. Am. Rod., 116, foot-note. |