MUSEUM OF COMPARATIVE ZOOLOGY. 217 



On the accompanying map the Pacific Province is colored pink, 

 the Central Province * blue ; the Eastern Province (of which the 

 northern portions are not shown) is uncolored. The subdivisions, or 

 regions, of the Eastern Province are also indicated by colored lines. 

 The red line marks the division between the Northern and Interior 

 Regions. From this line the last-named region extends (its Sub-Region 

 of the Cumberland shown by green lines) to the brown and yellow 

 lines, which, taken together, mark the northern boundary of the South- 

 ern Region, the yellow separately indicating the Texan Sub-Region, 

 the brown the Floridan Sub-Region. 



In the above pages I have simply stated the facts now known regard- 

 ing the actual distribution of our land shells, scarcely attempting to 

 explain it. I will here venture to make a few suggestions on this sub- 

 ject. 



Even at the present stage of our knowledge, we are justified in 

 believing that North America has received a group of small species 

 from the eircumpnlar regions. These species are common to the three 

 continents, Europe, Asia, and America. A great duration of time has 

 been required to effect their wide distribution over the continent, even 

 into Mexico. I believe, therefore, that they are no recent acquisition 

 to our fauna. They may even antedate the creation of our strictly 

 American species. f 



Again, in the Southern Region we have evidence of immigration 

 from other faunas ; Florida possessing West Indian and South American 

 species, Texas many from Mexico. We have, however, at the same 

 time, equal evidence of a distinct creation for a large portion of the 

 fauna of our Southern Region, so peculiar is it to the region. 



By a distinct creation only can I account for the origin of our pecu- 

 liarly American fauna of the Eastern Province. I have traced it to 



* On the map the dividing line between the Centra] and Eastern Provinces is 

 carried more easterly, above Lat. 40°, than described in the text. This is done on 

 account of the Central Province overlapping the Eastern at this point, as indicated 

 by the distribution of Patula strigosa. 



t Of these minute species common to the three continents, I find two at least, 

 Helix pulchella and Cionella subcylindrica, giving somewhat similar proof of great 

 antiquity by their distribution in Europe and Asia, and especially by their presence 

 in Madeira. 



