Oregon Freshwater Mollusca

From
Date
I'd like to repost my inquiry on freshwater mollusca, if there is 
anyone with a particular knowledge of these critters, especially in 
Oregon species, I would greatly appreciate any help.  I have run 
across problems in nailing down current names of my Fossil Lake 
population: Please reply via E-mail if you have any information 
(current taxonomy, ecologic factors, etc) of the following species:

Vorticifex effusa, Helisoma newberryi, Helisoma trivolvis, Valvata 
virens, Lymnaea stagnalis, and pisidid clams.

I have had particular difficulty in finding information on ecological 
factors in relation to V. virens.

I have noticed that almost all of the works on the above species are 
fairly old.Is this the norm? I would really like to compare shell 
measurements with recent studies to see how my samples compare with 
modern, stable lake environments.

Here's a few more questions to add insult to injury;  Has anyone 
noticed large shell variation in individual freshwater species? I have
read several older works that comment on this... and if
so are misnames a problem in small sample sizes? How about common 
adult sizes of the above mentioned specimens? I have several works 
that give different figures.

As stated before, I would greatly appreciate any help that may be out 
there. 

Cheers

Guy A. Hanley
University of Nebraska Museum Studies Graduate student