ATLANTIC STATES. 107 



Helix hortensis (imported), coast of New England and banks of St. Lawrence. 



„ pulehella (smooth var. only), Boston, Ohio, Missouri. 

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



„ para, nitida, and f ulva P 

 Zua lubrica, North West Territory. 

 Suocinea amphibia (= campestris, SayP). 

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



„ rtavus. New York, introduced. 

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

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



Aplexa bypnonmi (= elongata. Say?). 

 Auricula 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 Cydas have been obtained from the region of Lake Superior, 



The following species occur in New England : — 



Helix 13 Physa 2 TJnio 5 



Succinea 2 Planorbis 11 Alasmodon 2 



Pupa 7 Paludina 1 Anodon 2 



Limneea 7 Valvata 2 Cyclas 6 



Ancylus 2 Auricula 1 Pisidium 1 



Carychium exiguum, Say, is found in Vermont, and Limncea 

 (Acella) gracilis in Lake Champlain ; Valvata tricarinata and 

 Paludina decisa are characteristic forms, 



The genera Clausilia and Cyclostoma are entirely wanting in 

 Canada and the Northern States. The Limacidce are represented 

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

 from Massachusetts to Kentucky and South Carolina. 



17. 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 — the 

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

 About 50 fresh-water Puhnonifera, 150 pectinihranchiata, 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 Alleghanies. Cyclas mirabilis, Pisidium VirginicuMy 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, and 

 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 grows, 

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



