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Genera.

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Ursus ............
Callorbinus .......
Zalophus..........
Eumetopias.
Phoca .....
Pagomys ..........
Pagophilus ...........
Halichærus .........
Erignathus......
PELAGICS...........
Cystophora...........
CAMELUS............
Alces..............
Rangifer ........
Cervus ............
DAMA.............
ELAPHODUS ..........
LOPHOTRAGUS...

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CAPREOLUS ....

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MOSCHUS .....
HYDROPOTES ......
Bison .........
POËPIAGUS ....
ADDAX.....
Oryx.............
Gazella ...........
PROCAPRA ...............
SAIGA.....
PANTHALOP8 .......
BUDORCAS .....
RUPICAPRA....
Nemorhædus ........
Capra............
Ovis..........
Ammotragus ...
Sus ..........
Asinos. ..........
Rhinolophus..
Plecotus...........
Synotus............
Vesperugo..........
Vespertilio .........
Miniopterus .......
Taphozons .........
Rhinopoma ........
Nyctinomus ........
Erinaceus ..
Talpa.

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SCAPTOCHIRL'S...........
ANUROSO REX....
MYOGALE .......
NECTOGALE ........
Urotrichus.........
UROPSILCS .........
Sorez ..............
CRO:80PUS....
Crocidura .......
Mus...........
CRICETUS ..........
CRICETULUS...........
Meriones
RHOMBOMYS.......
PSAMMOMYS...
SMINTHUS .........
Arvicola ...........
Evotomys
MYOSPALAX..
ELLOBIUS ..........
SIPHNELS.
SPALAX ............
Dipus..........
ALACTAGA .........
MYOXUS ........
Moscardinus.......
Eliomye ...........
Castor ..........
Sciurus ...........
Tamias ............
Scirropterus .......
Pteromys ..........
Spermophilus .....
Arctomys ..........
Hystrix...........
Lagomys........
Lepus ..............

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Summary.

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......

rovince............ Genera occurring in the Western Temperate (European) Provi

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Genera occurring in the Eastern Temperate (Asiatic) Province..
Genera of the Mediterranean Province .....
Genera of the Manchurian Province.........
Genera common to the Eastern and Western Temperate Province..
Genera common to the Mediterranean and Manchurian Province
Maritime genera of the Asiatic coast........
Maritime genera of the European coast ........
Maritime genera common to both European and Asiatic coasts ...

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 differ. ence 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 Europæo. Asiatic 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 voticed) through the presence of genera limited to their southern subregions.

III.-AMERICAN TROPICAL REALM.

CON

The American Tropical Realm is approximately bounded by the northern and southern mean annuals of 70° F. Its northern boundary has been already indicated ia 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 contivues westward to the eastern base of the Andes. The Andean chain forms its western limit thence northward to Ecuador, wbere 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 defiderl, the southern border of the American Tropical Realm is nearly coincident with the southern boundary of the “ Brazilian

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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 Midido,= 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 Felido, except the Lynxes. It also has many peculiar genera of Glires and Chiroptera, while it almost alto. gether 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 Car. nivores, not only the Lynxes, but the true Wolves and Foxes, the Mar. tens, Wolverenes, Badgers, and Bears; among Ungulates, the Prong. horn, the Bison, Mountain Sheep, and Mountain Goat, and several important genera of the Cervidæ ; 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 provinent and characteristic genera of the order except the almost cosmopolitan genera Lepus and Sciurus; among Insectivores, all the Moles avd 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 Re. gion includes only the West Indies and the southern extremity of Flor. ida. The Central American Region embraces Mexico (exclusive of the elevated tablelands), the wholo 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 sub. cosmopolitan or tropicopolitan; about three-fifths range also over the Brazilian Region, and a few over nearly all of South America ; about one. half extend far into North America, among which are several that are also common to the greater part of the North Temperate Realın, 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

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feature is hence an approximately equal blending of temperate and tropical forms, whose respective habitats here overlap. Many of the Borthern 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.

Genera of the Central American Region.

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Summary.
Whole number of genera .............
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

World ..
Subcosmopolitan ......
Tropicopolitan ...

Antillean Region. The Antillean Region differs from both the Cen tral American and Brazilian most strongly in negative charactersthrough what it lacks rather than in what it has-although it pos: sesses a number of peculiar genera. The Chiroptera form two-thirds of the genera and not less than five-sixtbs of the species. Of the eight peculiar genera, five are Bats, the others being Solenodon (the only 10. sectivore), Capromys, and the closely allied Plagiodonta, which together

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