28 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



The species peculiar to Greenland are Vitrina Angelica?, Zonites 

 Fabricii, Pupa Hoppii, and Succinea Groenlandica. Of these, Pupa 

 Hoppii has, however, also been found on Anticosti Island. 



Into this Northern Region have also been introduced by commerce 

 from Europe the following : Zonites cellarius, at most of, if not at all 

 of, the ports from New York to Halifax; Limax flavus, L. agrestis, and 

 Avion fuscus, which follow the white man over the whole United States, 

 living around his habitations ; and L. maximus, also around human 

 habitations, but noticed only in Newport, R. I., New York City, and 

 Philadelphia; Fruticicola hisjrida at Halifax, F. ntfescens at Quebec; 

 Tachea hortensis on the islands off the coast of New England and the 

 British Provinces, and on the mainland in Canada and Greenland. 



Of the species referred above to the Northern Region, several have 

 spread beyond its limits. Vitrina limpida has been found in Central 

 New York ; Zonites viridulus extends to Mexico ; Z. milium to San 

 Francisco and Kentucky ; Z. fulvus and Vallonia pulchella all over the 

 United States ; Zonites nitidus, Z. mrdtidentatus, and Punctum minutis- 

 simum to Ohio, the last to Texas and to California ; Ferussacia subcylin- 

 drica to the States south of the Great Lakes and into California and 

 New Mexico ; Patula striatella to Virginia, as well as into Oregon and 

 Nevada. 



The Northern Region does not differ in the characteristics of its fauna 

 from that lying south of it, but its climate is too severe for any but the 

 more hardy forms. Thus, we find only the small species of Zonites and 

 disintegrated Helix, with the genus Vitrina. Compared with the bal- 

 ance of North America, the Region is peculiar for the great distribution 

 of its species east and west, owing to the mountain-ranges having here 

 lost the great elevation which they have farther south, and thus ceasing 

 to be barriers to distribution. The Region is also interesting as being 

 the source from whence have spread southward over the whole conti- 

 nent several small species now found in Florida and Texas, and even in 

 Mexico and the West Indies. 



(b.) The Interior Region lies to the south of the Northern Region, 

 but extends only as far as the Rocky Mountains 1 on the west. South- 

 erly it extends to the alluvial regions of the Atlantic and Gulf coasts, 

 the dividing line here not being sharply defined. 



This is the only portion of the continent where we have evidence of 



1 This is the extreme limit, but before reaching it the land shells have become very 

 rare, owing to the nature of the soil. For a description see Vol. I. 1. c. 



