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VALLONIIDAE 



Family VALLONIIDAE 



Snails belonging to the family Valloniidae are abundant in 

 Illinois, although only one genus of this family, Vallonia, is 

 found in the state. 



Genus VALLONIA Risso 



Shells of the genus l^allonia are small in size ; none of them 

 exceeds one-eighth inch (2.75 mm.) in diameter, and several 

 are smaller (2.0 mm.). In color most of the shells are waxy 



white, although some are reddish or brownish. Shells in some 

 species are dull; in others they are shiny or glassy in appearance. 

 Shells in this genus are flattened or only slightly elevated, and 

 in most species the ZV2 or 4 whorls seem to be coiled in the same 

 plane. This structure, which allows all of the whorls to be seen 

 from the underside, forms a very broad umbilicus. The aperture 

 varies in shape, being either round or oval. The peristome is 

 reflected, as in the large Polygyra snails. The Valloniidae have 

 no folds or lamellae within the aperture. In some species the 

 surface of the shell is covered with thin, membranous ribs 

 which are evenly spaced and stand erect from the surface of 

 the whorls. In other species the surface is marked only by 

 rounded ribs formed by the growth lines. 



The animal is small in size and yellowish white in color. 

 The cylindrical eye peduncles are not enlarged at the end as 

 In Sfrobihps: the tentacles are short. When the animal is 



