248 YALLONIA. 



Vallonia is widely distributed over the northern part of the old 

 and new continents, extending to northern Africa, the Atlantic 

 islands, Indo-China, and the southern United States. It has been 

 found in Australia and Mauritius, undoubtedly introduced, as it prob- 

 ably is or will be in other suitable localities. Geologically it is an 

 old form of Helicidse. It is a common fossil in the Loess of Europe 

 and North America, and in Europe has been found in lower Eocene 

 strata and many subsequent deposits. In this antiquity of the genus, 

 we find the key to its wide geographic distribution. 



These small snails live in moss and among dead leaves, under 

 decaying wood and stones and are very sensitive to light. By heavy 

 rains the dead shells are washed down and are sometimes found in 

 immense numbers in fine drift material along streams and rivers. 



In characters of the shell and the soft parts, Vallonia is a well 

 defined genus. The features are very uniform, and the comparatively 

 large number of species now known require close attention to distin- 

 guish them. A few certainly will need revision, but most of them 

 appear to be valid. A single species, the F pulchella of Miiller, 

 has been recognized generally for almost a century ; and F costata 

 having been regarded as a ribbed variety, it is evident that all the 

 older reports as to geographical distribution must be received with 

 reserve, as necessarily quite a number of different forms were com- 

 prised under one or two names by the older authors, and by some 

 even up to the present day. 



(1) Group of V. pulchella. 



Aperture crescentic, forming about five-sixths of a circle ; surface 

 very finely striated. 



V. PULCHELLA Miiller. PI. 32, figs. 1, 2, 3, 4, 5. 



Moderately umbilicated, more widely for the last half whorl ; con- 

 vex or depressed conic above ; straw colored, transparent, with fine 

 and dense strice which are more regular at the suture and umbilicus ; 

 smooth at the nucleus; whorls 3s-4, rather rapidly increasing, witn 

 a moderately deep suture, the last comparatively large, well rounded, 

 little expanded toward the aperture, not descending in front, or 

 slightly so at the suture. Aperture moderately oblique and inclined, 

 forming five-sixths of a circle ; peristome abruptly everted, with a 

 strong white lip, thinner at either end. 



Alt. 1*2, greater diam. 2*4, lesser 2'0 mill. 



