254 PROCEEDINGS OF THE ACADEMY OF [1893. 



variability in the transparency of the shell — the New York and 

 New England specimens are, as a rule, more glassy and shining 

 than those from Washington, D. C. and from Europe. 



In a lot of Vallonia from the Pyrenees (no special habitat or 

 region is noted), belonging to the Academy Collection, there was 

 one poor weathered specimen of V. pulchella and a number of V. 

 costata, together with a peculiar variety, and the present form, 

 which then struck me for the first time as probably being a distinct 

 species. 



At Washington, D. C, I collected in February and again in 

 March, 1889, under granite stones, numerous Vallonia which then 

 were simply placed as pulchella. Many of those collected there 

 in March, under bricks in an old brick-yard were in company 

 with Hyalinia minuscula Binn., and Pupa procera Gould, of 

 which, it may be mentioned, I secured about 800 specimens in 

 a few hours by brushing the bricks. When I began to study 

 Vallonia specially, these shells were looked over carefully, 18 and 

 then I was surprised to find both species, pulchella and the one 

 under consideration, in both of the two former lots, while those from 

 the brick-yard were pulchella exclusively. They were so exactl} r 

 like the Pyrenean shells that there could not be the least doubt as 

 to their identity ; they were so distinct from pulchella as to be sep- 

 arated one by one at first glance, there being no doubtful or inter- 

 mediate examples. Subsequently I looked over every specimen of 

 more than 90 parcels of Vallonia containing either pulchella or the 

 new form, or both, coming from Europe and North America, and 

 the result was to establish the certainty that the present is a good 

 species, for which I propose the name V. excentrica. It is of a wide 

 geographical distribution, its shell being readily discerned when 

 once attention has been directed to its peculiarities. But it must be 

 added that specimens are found occasionally in which the distinc- 

 tion is somewhat obscure ; these are generally small pulchella which 

 had been damaged and restored more or less imperfectly, with little 

 everted peristome. I have several such examples : one from Illinois 

 which, at first sight, would be taken for excentrica, but by close 

 examination proves to be pulchella. On the other hand, one exam- 

 ple of V- excentrica, from Washington, D. C, has a rather strongly 

 everted lip, caused by a breakage near the aperture. 



It is somewhat surprising that this form has been overlooked in 



18 As I have sent specimens to several conchologists, they should now be revised. 



