364 GEOLOGICAL SURVEY OF THE TEEEITOEIES. 



clearer and more concise ideas of tlie geographical distribution of life 

 on our continent.* 



The following two species of Phyllopods characterize this realm : 

 Lepidurifs glaciaUs, Arctic America, Lapland, KovaZembla, Spitzbergen, 

 Beeren Island ; and Brancliinecta paludosa. Neither of these are confined 

 to the American continent (being found at Cape Krusenstein) and Green- 

 land, as they occur in Arctic Europe 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 Eussian Lapland, and Middendorf 

 found it (var. middendorjianus) in Asiatic Siberia. 



THE ATLANTIC OR EASTERN PROYINCE. 



This region includes the area bounded on the north by the isothermal 

 of 40°, includiug 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: 



Limnetis gouldii. Estheria mexicana. 



{Limnodella coriacea.) EuUtnnadia agassizii. 



Limnadia americana. BrancMpus nernalis. 



Streptocephalus sealii. serrotus. 



Jioridanus. ChiroGeplialus liolmani. 



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 Eocky Mountains oppose no continuous barrier to the distribution 

 of the species ; and it includes the southern extremity of the Californian 

 i:)eninsula. We reproduce from the American Naturalist fbr August, 

 1878, the leading characteristics of this Central province. 



The first attempt to divide the United States as a whole into zoolog- 

 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 zoolog- 

 ical districts, distinguished each by numerous peculiar genera and 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., 18t)6, 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. This is a trae circum- 

 jjolar 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 18.56 ; 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 deirths, the necessary amount of cold for their existence." 



Compare also onr monograph of Geometrid Moths, or Phalteuidae, 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, etc.. Bull. Mus. Comp. Zool. ii, 3, 1871, Bull. Haydeu's U. S. Geol. Survey, 

 1878, p. 529. 



