Grebneff's message on sinistral shells reminded me i wanted to ask how
common are sinistral knobbed whelks?  i don't know whether the normal is
right or left-handed, but i found in my collection i have two
identical-sized large knobbed whelks which are mirror images of each
other.  which one is the normal and which isn't, and how common are they
and how much is the abnormal shell worth?
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Steve
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