> ----------
> From:         Martin S. Kohl[SMTP:[log in to unmask]]
> Sent:         vrijdag 12 februari 1999 4:59
> To:   [log in to unmask]
> Subject:      Corbicula varieties
> 
> Hello All;
> 
> I've picked up some Corbicula during some recent walks along the Tennessee
> River (yes, it's come to that, Unios are getting so scarce) and noticed
> there
> seems to be two distinct varieties, differentiated by a consistent set of
> characteristics.  Variety "2" is more inflated, thicker shelled, has a
> more
> strongly projecting umbo, a more sharply curved posterior corner, and the
> lateral teeth diverge at less than 90°, giving the shell a more strongly
> triangular outline.  Variety "1" has the opposite features.  The relative
> abundance of the two varies from place to place, but "1" is usually more
> abundant.  Intermediate ones are not too common, and I did not see any
> with
> mixed characteristics.
> 
> Also, many of the older corroded shells are much larger than the more
> recent
> ones.  Does anyone have an opinion on these variations?
> 
> Thank you for your interest,
> 
> Martin Kohl
> 
Also here in  the Netherlands there exist two species of recently introduced
Corbicula's, one with relatively broud ribs, called C. fluminea, and a form
with narrow ribs, C. Fluminalis. On the beach you can find fossil
Corbicula's, they don't fit these two newly introduced species. Martin Cadee
(The Netherlands)