Of course some common shells are SO common (Donax variabilis seething in
swash) that nobody first seeing them in their habitat could possibly think
them rare. But when the shells are at the botton of a 600m-deep canyon it's
another story. Even species that are abundant in hard-to-reach places will
be rare in collections due to lack of availability. Look at hydrothermal
vent faunas! Abundant locally, but pretty scarce in dealers' catalogs. An
example could be a new species of Epitonium (Gyroscala) that I discovered
last year; all of the 20-odd specimens are currently in my collection (only
3 are even largely complete) but all came up in one dredgeload of mud. They
must be there in some numbers, abeit very local, as other hauls have not
yielded any.

And yes, some shells really ARE rare even in their habitats. This is often
the case with epitoniids. Solitary shells may turn up once in many cubic
meters of suitable dredgings, such as the new Acirsa that was in the same
dredgehaul as the above Epitonium; likewise the sole A. cookiana that was
with them. Why should some species be abundant while other related species
are rare? I doubt we will ever really know.

Andrew (a seemingly abundant taxon in the Conch-L matrix)