Neither the operculum nor the parietal area color works every time.
Clenchi is generally more globose (lower spired) with a substantially
thinner shell (per unit size).  The color pattern of clenchi is less
variable consisting of the axial lines with little light colored triangles
or dots.  I admit that it is almost a gestahlt thing, but if you look at
enough it becomes very clear.  Again, clenchi is freshwater, virginea
brackish.
Kurt
 
At 08:18 PM 3/9/98 -0500, you wrote:
>You said the differences between N. virginea and N. clenchi were in the
>color of the operculum and the color of the parietal area.  Can you give us
>more details?
>
>----------
>> From: Philip Poland <[log in to unmask]>
>> To: [log in to unmask]
>> Subject: N. clenchi
>> Date: Monday, March 09, 1998 6:01 PM
>>
>> I took a look at Matheson Hammock specimens being offered as N. clenchi,
>> and am convinced that they're N. virginea. If anyone has these, or other
>> specimens they aren't sure of, perhaps Kurt or someone else familiar with
>> the species could verify the identification.
>