ATLANTIC STATES. 107 



Helix hortensis (impoi-ted), coast of New England and banks of St. Lawrence. 



„ pulchella (smooth var. only), Boston, Olxio, Missouri. 

 Helicella cellaria (glaplijTa, Say?), N. E. and middle States. 



„ pura, nitida, and fulva? 

 Zua lubrica. North West Territory. 

 Snccinea amphibia (= campestris, Say?). 

 Limax agrestis (= tunicatus, G-.), Mass. 



„ tiavus. New York, introduced. 

 Vitrina pellucida (= Americana?) Limnaea palustris (= elodes. Say?). 

 Aiion hortensis, New York (Dekay.) „ truncatula (= desidiosa?). 



Aplesa bypnorum (= elongata, Say?). 

 Aui-icnla deticulata, Mont., New York Harbour. 

 Alasmodon margaritiferus (= arcuatus, Barnes). 

 Anodon cygneus (= fluviatilis. Lea?). 



The shells proper to Canada, or derived from the adjoining 

 States, are only 6 sp. of Helix, 2 Succineas, and 1 Pupa ; 8 sp. 

 of Ci/clas haye been obtained from the region of Lake Superior. 



The following species occur in New England : — 



HelLx 13 Physa 2 Unio 5 



Succinea 2 Planorbis 11 Alasmodon 2 



Pupa 7 Paludina 1 Anodon 2 



Limneea 7 Valvata 2 Cyclas 6 



Ancylus 2 Auricula 1 Pisidium I 



Carycliium exiguum, Say, is found in Vermont, and LimncBa 

 (Acella) gracilis in Lake Champlain ; Valvata tricarinata and 

 Paludina decisa are characteristic forms. 



The genera Clausilia and Cydostoma are entirely wanting in 

 Canada and the Northern States. The Limacidce are represented 

 by Philomycus, of which there are 9 reputed species, ranging 

 from Massachusetts to Kentucky and South Carolina. 



n. Atlantic States. 



The parallel of 36® N. lat. forms the boundary-line of two 

 botanical regions in the United States ; but the evidence of the 

 fresh- water shells, in which they are particularly rich, seems 

 to favour a division into two hydrographical provinces — tho 

 region of the Atlantic streams and the basin of the Mississippi. 

 About 50 fresh- water Pidmonifera, 150 pedinibraiichiata, and 

 250 bivalves, are reputed to be found in the States, and it is 

 supposed that only a few species are common to both sides of 

 the AUeghanies. Cydas mirabilis, Pisidium Virginicum, Cyrena 



3,000 feet on the mountains of Scotland. (Watson.) According to Pallas it abounds 

 on the western flanks of the Ural Mountains, but disappears on their eastern side, an<f 

 IS not found in Siberia. In the Pliocene period it appears to have spread itself north 

 ward and westward to Iceland, Greenland, and Newfoundland, where it still gi'ows, 

 the only heath indigenous to the New World. (Hiunboldt.) 



