Recently someone posted a message requesting the common names of three
species of pectens (scallops).  I posted a reply, offering common
names for two of the species, taken from the Compendium of Seashells.
 There are a few things we should keep in mind about common names.
First, an overwhelming majority of the known molluscan species do not
have any common name at all.  It is primarily the better known species
in the better known families that have been given common names.
Practically all the cowries (family Cypraeidae) have generally
accepted common names (at least in english).  Probably only 1/2 to
2/3 of the cones (family Conidae) do, and practically none of the
hundreds of described turrids (family Turridae) have common names.
The Compendium of Seashells lists an english name for every one of
the 4,400 or so species pictured, which could lead a novice collector
to expect that every species has a generally accepted common english
name.  But frankly, many of the common names listed in the Compendium
were not in general usage, or did not exist at all, before publication
of the book; and many of them are still not in general usage today.
Many of these names were created specifically for that book.  I don't
mean this as a negative criticism - it is simply a statement of what I
believe to be fact, not a judgement.  Actually, I think the inclusion
of so many interesting common names gives the book much greater
appeal to the general public.  In many cases, the author formed the
listed common name simply by translating the scientific name, which
is always a preferable way of selecting a common name, when the
resulting translation makes logical sense.  For example, he calls
Chlamys flabellum the "African Fan Scallop" because "flabellum"
literally means "fan", and the species comes from west Africa.  In
other cases, he used either a physical characteristic of the shell,
or its geographic locality as the basis of the common name.  On the
one hand, this points to the desirability of familiarizing ourselves
with scientific names.  On the other hand, it also points out that
common or vernacular names are not "binding" in the sense that
scientific names are.  If you are preparing a scientific exhibit for
a shell show, and can't find the scientific name of an included
specimen, it would not be acceptable to simply make one up.  Doing so
would convey objectively false information to persons viewing the
exhibit.  However, in preparing a display for the general public,
where vernacular names would be more meaningful than Latin names, you
don't have to get frustrated if you can't "find the common name" for
one of your specimens.  Perhaps there isn't a generally accepted
common name.  What do you do?  Leave the shell out of the exhibit?  I
wouldn't!  Once I established that no generally accepted common name
exists, I'd just make up an appropriate common name.  No special
training or authority is needed to do this.  No-one can say you are
using the "wrong" name, if there isn't any "right" one.  Indeed,
widely accepted common names were not assigned by scientists, but
were created by the ordinary folks who speak the language.  Case in
point - getting back to the three scallops for which common names
were requested -  the third species was, if I recall correctly,
Chlamys crassicostata.  This species is not pictured in the
Compendium, and I doubt that you are going to find a published
english name for that species.  However, if it HAD been included in
the Compendium, it would have been listed as "thick-ribbed scallop"
or perhaps "stout-ribbed scallop", because "crassi-" means "thick" or
"stout", and "costata" means "costate", or ribbed.  So that name is as
valid as any other, as a common name for this species.
Regards,
Paul M.