CHAPTER XXXIX: THE RIVER SNAILS 



Family Streptomatidv^ 



Shell turreted or ovate; aperture angled or channeled 

 in front; epidermis olive-hued; operculum sub-spiral; mantle 

 not fringed. An oviparous group of five hundred species, con- 

 fined to the United States except for a few West Indian species. 

 They are found chiefly in the headwaters of streams rising in 

 the mountains of the south central states. 



Genus lO, Lea. 



Shell tuberculated, with few exceptions; spire elevated; 

 peristome flaring; canal twisted; columella smooth, concave. 

 Few species in rivers of Tennessee and West Virginia, 



The Spiny lo (/. spinosa. Lea) is the most graceful of these 

 tuberculated fusiform shells, quite as beautiful in form as the 

 spindle shells it resembles. Under the horny epidermis obscure 

 purplish bands appear on an olive ground. The aperture is half 

 as long as the shell. Length, 2 inches. 



Habitat. — Virginia, Tennessee. 



The prominence of the tubercles makes this species pre- 

 eminent among American river snails, and leads to their being 

 mistaken for marine mollusks. Specimens found in Indian 

 graves were called "conchs" by their discoverers, who argued 

 that the tribes must have once lived near the shore. But no 

 such shells occur in salt water. 



The River lo (I.fluviatilis, Lea) is smooth or faintly knobbed, 

 solid, greenish, stained with purple. The canal is scarcely 

 twisted and has a rounded end. Length, i inch. 



Habitat. — Tennessee region. 



I. inermis, Anthony, is unarmed. The smooth, elegantly 

 fusiform shell is purplish throughout. Length, 2 inches. 



Habitat. — Southern States. 



The Turreted lo (/. turrita, Anthony) is more elongated 



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