AURICULACEA. 155 



bilobed snout. The mantle is thin, thickened on its mar- 

 gin. The foot is elongated and pointed. The sexes are 

 united in each individual. 



The shell is spiral, extremely variable, and in the Amer- 

 ican species conic, generally with a flattened spire, and 

 furnished with numerous tooth-like laminae, which con- 

 tract the narrow aperture. 



The Auriculidce are amphibious Mollusks, breathing 

 free air, but apparently dependent for existence on a great 

 deal of moisture, if not on the actual vicinity of the sea. 

 Some species pass their whole life under circumstances 

 which seem to preclude the possibility of their respiring 

 air. Thus Alexia myosotis is often found on isolated 

 stones in salt marshes, which are entirely covered by the 

 tide four hours out of twelve. This species, when im- 

 mersed in fresh water, becomes benumbed and soon dies. 



Carychium exigmun, on the other hand, though found 

 under similar circumstances, does not depend on salt 

 water, being widely distributed far beyond its influence 

 over the interior of the country. Blauneria pellucida also 

 has been detected living far from any water in a garden 

 in Washington, whither it was introduced on plants from 

 Charleston, S. C. With the exception of the two last 

 mentioned, the American species are found on salt marshes 

 and in brackish water near the sea. 



Of their geographical distribution but little is yet known. 

 Melampus bidentatus is found from Maine to Florida. 

 Melampus obliquus is referred by Say to South Carolina. 

 Alexia myosotis was probably introduced from Europe, 

 I have never known of its being found south of New 

 York harbor. Carychium exiguum will probably be found 

 in all the Middle and Northern States. The other species 

 are confined to the coast of Florida and the Gulf of 

 Mexico, some of them being common to Cuba and other 

 West Indian Islands. 



