1906.] NATURAL SCIENCES OF PHILADELPHIA. 531 



From the investigations made by the authors and their friends, it is 

 obvious that there was in the East no extensive glacial recession 

 of the snail fauna southward beyond the border of the ice sheet. It 

 seems likely that the northern fauna of Appalachian origin was largely 

 wiped out, and the survivors crowded with the boreal forms in a band 

 along the States bordering the glaciated area. This comparatively 

 recent concentration of the snail population southward gives at first the 

 impression that the radiation of this element of our fauna was from 

 the southeast, yet during the mild tertiary period favorable condi- 

 tions certainly existed much farther north than at present, and 

 there seems no more reason to postulate a southeastern than a north- 

 eastern tertiary radiation. 



In the more elevated Rocky Mountain region there was obviously a 

 more extensive glacial recession. Boreal genera and species were 

 pushed at least as far as the Mexican boundary, where they still sur- 

 vive at considerable altitudes. 



The Appalachian types of land snails now extend over all of the Alle- 

 ghanian, Carolinian and Austroriparian zones ; but within this area we 

 must recognize several strongly individualized faunas characterizing 

 mountainous tracts. These are as follows : 



I. The Austro-Appalachian faima, comprising the eastern division of 

 the Appalachian Mountains east of the valley of East Tennessee chiefly 

 in North Carolina, south to Georgia. It is bounded on the north in 

 Virginia and West Virginia by an Alleghanian zone fauna on the high- 

 est ridges and a normal Carolinian at lower levels. The Austro- 

 Appalachian fauna has been explored by Dr. Rugel, Mrs. George 

 Andrews, Mr. Wetherby, Messrs. Walker, Sargent, Clapp, and the 

 present authors. It is mapped as Transition and Boreal in Dr. 

 Merriam's Life Zone map of 1897. 



II. The Cumberlandian fauna, including the western division of the 

 Appalachian Mountain system in Kentucky, Tennessee and northern 

 Alabama. The limits of this fauna extend southwestward beyond the 

 nucleus plotted as Transition in Merriam's map. Our knowledge of 

 this fauna is due to Lea, Binney, Bland, Wetherby, Harper and others. 

 It has been neglected by the present generation of conchologists, but 

 ■careful collections by Mr. and Mrs. H. H. Smith are now in progress 

 on its southern border (Alabama). 



III. The Ozarkian fauna, limited to the Ozark uplift, chiefly in 

 Arkansas, but extending into adjacent States north and west. It is 

 largely mapped as humid Upper Austral ( = Carolinian) by Merriam. 



These three faunas possess but few species in common, aside from 



