108 MAlTTrAI OF THE MOLLUSCA. 



CaroUnensis, and Unio complanatus and radiatuB, are cliaracter- 

 istic of the eastern rivers; Melania depygis is said to be th© 

 only member of that large genus found eastward of the Hudson 

 Eiver. Of the American land-snails, 29 sp. of Helix, 6 Suc- 

 cineas, and 13 Pupas are enumerated from the Atlantic States, 

 In Florida the propinquity of the "West Indian fauna is strongly 

 indicated by the occurrence of the great Olandina truncata, by 

 species of Cylindrella, and a Helicina. A Cuban species of 

 Chondropoma (0. dentatum) is also said to occur in Florida, and 

 Ampidlaria depressa in Florida and Georgia. 



The Pidmonifera of North America have been carefully exa- 

 mined by Messrs. Binney,* Bland, f and others. The following 

 summary of North American PwZmowt/era is given by Mr. Binney. 

 The area is nearly co-extensive with our regions, Nos. 16 

 and 17. 



Arion 2 Bulimus 21 Melampus 11 



Limax 3 Achatina 5 Carychium ,.,. 1 



Philomycus 2 Pupa 12 Limnsea 34 



Vitrina 2 Vertigo 4 Physa 19 



Succinea 18 Cylindrella 4 Planorbis 21 



Glandina 6 Veronicella 1 Ancylus 10 



Helix 131 



There are also found in the fresh waters of this district Mela^ 

 niadcB 380, Faludinidce 58, Cycladidce 44, Unionidce 552. 



18. American Eegion. 



The mass of American land and fresh- water shells are found 

 in the central and southern States, the country drained by the 

 Mississippi and its tributaries. The Helicidos, are not more re- 

 markable for size and colour than those of northern Europe ; 

 the most characteristic forms belong to the sub-genus Polygyra 

 (or Tridopsis, Eaf.), such as Helix tridentata, alholabris, hirsuta, 

 and septemvolvis. The truly North American forms all belong 

 to three genera, viz. — Helix 43, Succinea 8, Pupa 3 species. 

 In the Southern States are also found 5 species of Bulimus, 

 3 Cylindrellas, 2 Glandinas, and 5 Helicinae, genera whose 

 metropolis is in the Antilles or in tropical America. 



The fresh- water univalves include above 100 species of Mela- 

 niadce belonging to the genera Ceriphasia, Melafustbs, Anculotua, 

 Melatoma, and Amnicola, 15 Faludince, some keeled, and one 



* In several papers in Proc. Acad. Nat. Sci. Phil, 1857, and subsequent years, 

 t Remarks on the Classification of N. Am. Helices. Annals of Lyceum of Nat. Hist., 

 New York. 1863. 



