G. GENERAL NATURAL HISTORY AND ZOOLOGY. 321 



and but two are recognized in the Eastern province. The 

 hrst of these is the northern region^ embracing the whole of 

 the northern portion of the continent, including Greenland 

 and Alaska, and extending southward about to the borders 

 of the United States, and running down the Appalachian 

 chain of mountains to Chesapeake Bay, thus including all of 

 New England, a portion of New York, New Jersey, Pennsyl- 

 vania, and Maryland, lying east of the Alleghanies. The en- 

 tire region lies to the south of the northern region, but ex- 

 tends only to the Rocky Mountains on the west. Southward 

 it reaches the alluvial region of the Atlantic coast, the divid- 

 ing line not being very sharply defined. 



The southern region embraces the peninsula of Florida, 

 with the adjacent islands, together with the alluvial region 

 of the Atlantic and Gulf States. 



Some sub-regions are recognized in the principal regions, 

 the most important of w^hich is one called the Cumberland. 

 This covers the southern portion of the Appalachian chain 

 situated in East Tennessee, and the adjoining portion of 

 North Carolina, Avitli an oflfshoot into the mountains of West 

 Virginia. It is in this sub-region that we find the largest 

 number of species of land shells in any portion of North 

 America, or ninety in all. Of these, twenty-four are peculiar 

 to it, while sixty-six inhabit other portions of the interior re- 

 gion. It is equally prolific in individuals, which, too, are 

 liighly developed. This is explained by the nature of the 

 country, which consists of low mountains, thickly wooded, 

 well watered, and with a genial climate and fertile soil. A 

 peculiar feature of this Cumberland region consists in the 

 tendency to carination of a large number of its species. 



It is in the interior region alone, according to Mr. Binney, 

 that we have any evidence of the existence of land mollusks 

 in former Gfeolourical times, immense numbers of shells oc- 

 curring in the post-pliocene deposits of the Ohio and Mis- 

 sissippi Rivers. 



In regard to the origin of the land shells at present found 

 in North America, Mr. Binney believes that a small group 

 has been received from the circumpolar regions, certain spe- 

 cies existing that are common to America, Europe, and Asia. 

 He thinks a long period of time has been required to effect 

 their distribution over the continent, and that they are not a 



02 



