VALLONIIDAE 



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VALLONIA COST ATA (Muller) 



The snail Vallonia costata, about the size of Vallonia pul- 

 chella, may be recognized by the series of regularly spaced 

 membranous ribs which mark the surface of the shell and are 

 conspicuous on the body whorl. This 

 whorl angles downward a trifle near 

 the aperture. The shell of this species 

 measures over one-sixteenth inch (2.5 

 mm.) in diameter. The spire is flat- 

 tened, and all the whorls are visible 

 in the rounded umbilicus. The aper- 

 ture is rounded, and the white peri- 

 stome is wide and flat. In color the 

 shell is usually gray, but in some speci- 

 mens it is reddish. 



The costate Vallonia is apparently 

 rare in Illinois and is known from only 

 the northern half of the state. Its 

 usual habitat appears to be on floodplains in river valleys, but 

 specimens have been found on a railroad embankment near 

 Champaign, representing a prairie habitat. Champaign County is 

 the southernmost area from which specimens have been reported. 



VALLONIA PARVULA Sterki 



About one-sixteenth inch (1.5-2.0 mm.) in diameter, J'allonia 

 parvula has an umbilicus proportionately larger than that of 

 / allonia costata. The spire is less elevated, and the last whorl 



does not angle downward so abruptly 

 near the aperture as in costata. The 

 color is a dull waxy white. 



The Illinois habitats of J allonia 

 parvula vary from woodlands adjoin- 

 ing small lakes to bluffs of the Ohio 

 and Mississippi rivers. Oak, elm and 

 hickory are the forest trees most usu- 

 ally present in these localities. The 

 species is found on small sticks and 

 on the bark of logs. It has about the 

 same distribution as costata. 



