364 GEOLOGICAL SURVEY OF THE TERRITORIES. 
clearer and more concise ideas of the geographical distribution of life 
on our continent.* 
The following two species of Phyllopods characterize this realm: 
Lepidurus glacialis, Arctic America, Lapland, Nova Zembla, Spitzbergen, 
Beeren Island; and Branchinecta paludosa. Neither of these are confined. 
to the ‘American continent (being found at Cape Krusenstein) and Green- 
land, as they occur in Arctic Kurope and Asia. These two species oc- 
cur not only in Greenland and Arctic America, but also in Swedish 
Lapland at an elevation of 2,000 feet; Branchinecta paludosa occurs in 
Finmark near the North Cape and in Russian Lapland, and Middendorf 
found it (var. middendorfianus) in Asiatic Siberia. 
THE ATLANTIC OR EASTERN PROVINCE. 
This region includes the area bounded on the north by the isothermal 
of 40°, including the northern shore of the Saint Lawrence west of Que- 
bec, the Great Lake region, except the northern shores of Lake Superior, 
and the United States east of the ninety-seventh meridian.. 
The following species inhabit this province: 
Tamnetis gouldii. Hstheria mexicana. 
(Limnadella coriacea. ) Hulimnadia agassizit. 
Limnadia americana. Branchipus vernalis. 
Streptocephalus sealia. serratus. 
floridanus. Chirocephalus holmant. 
THE CENTRAL PROVINCE. 
This province lies between the Atlantic and the Californian, extend- 
ing northward into British America to the limits of trees near latitude 
55°; and southward along the Mexican plateau as indicated on the map. 
The Rocky Mountains oppese no continuous barrier to the distribution 
of the species; and it includes the southern extremity of the Californian 
peninsula. We reproduce from the American Naturalist for August, 
1878, the leading characteristics of this Central province. 
The first attempt to divide the United States as a whole into zoélog- 
ical provinces was in 1859, by Dr. Le Conte, in his “‘ Coleoptera of Kansas 
and Eastern New Mexico (Smithsonian Contributions, 1859).” He di- 
vided the Coleopterous fauna of the United States into three great zodlog- 
ical districts, distinguished each by numerous peculiar genera vand species, 
which, with but few exceptions, do not extend into the contiguous dis- 
tricts. He named them the Eastern, Central, and Western divisions ; 
*In our ‘‘Observations on the Glacial Phenomena of Labrador and Maine,” etc., 
Mem. Bost. Soc. Nat. Hist., 1856, p. 254, we thus referred to this fauna, speaking espe- 
cially of the marine animals: 
“The arctic or circumpolar fauna is restricted to a district north of the yearly iso- 
thermal line of 32°, which thus includes the Arctic American archipelago, Northern 
Greenland, Spitzbergen, Nova Zembla, and the coast of Siberia. Thisisatrue circum- 
polar fauna, and can scarcely be said to be Asiatic, European, or American, though 
members of the group extend in diminished numbers and size down on the Asiatic 
coast to Japan, as we are informed by Dr. W. Stimpson, and by P. P. Carpenter in 
the Report of the British Association for 1856; on the European coast as far as the 
Mediterranean Sea, and on the eastern American coast as far as New Jersey, where the 
polar currents give, at great depths, the necessary amount of cold for their existence.” 
Compare also our monograph of Geometrid Moths, or Phalenide, of the United States, 
pp. 567, 586, 1876. Our Classification of the American fauna is adopted with slight 
“modifications from Mr. J. A. Allen’s writings on the Mammals and Winter Birds of 
Florida, ete., Bull. Mus. Comp. Zodl. ii, 3, 1871, Bull. Hayden’s U. S. Geol. Survey, 
1878, p. 529. 
