New Species - Brown-lipped Snail

I have identified and blogged a slug species before (the Green Cellar Slug) but not any snails so when I came across a whole bunch of them under a roof tile in the barn I thought I ought to make a start. These appear to be the common Brown-lipped Snail (Cepaea nemoralis). I read that snails are hermaphrodite but need to mate to reproduce. That seems to be an efficient evolutionary trait - maximise the opportunities to reproduce but ensure genetic viability.