Back in antiquity (1968) R. Tucker Abbott published his Guide to Field
Identification - SEASHELLS of North America.  In it Tucker indicated that
the phylum Mollusca included "about 100,000 living species."  Few today
would disagree that Tucker significantly underestimated.  Some current
estimates include 250,000+.  There are eight living classes
<http://en.wikipedia.org/wiki/Class_%28biology%29>  of molluscs.
Caudofoveata <http://en.wikipedia.org/wiki/Caudofoveata>  - small, deep-sea,
worm-like creatures  <http://www.meer.org/Mindx.htm> that live buried head
down in the sea floor; 70 known species; now generally recognized as a
subclass of Aplacophora
Aplacophora <http://en.wikipedia.org/wiki/Aplacophora>  - small deep-sea,
worm-like creatures  <http://www.meer.org/Mindx.htm> that live symbiotically
or feed upon cnidarians.  They have no shell, eyes, or tentacles. 250
species.  Also known as Solenogasters.
Polyplacophora <http://en.wikipedia.org/wiki/Polyplacophora>  - chitons; 600
species, found on rocky marine shorelines
Monoplacophora <http://en.wikipedia.org/wiki/Monoplacophora>  - deep-sea
limpet-like creatures; 11 living species
Pelecypoda (Bivalves) - clams <http://en.wikipedia.org/wiki/Clam> , oysters
<http://en.wikipedia.org/wiki/Oyster> , scallops
<http://en.wikipedia.org/wiki/Scallop> , mussels
<http://en.wikipedia.org/wiki/Mussel> ; 8,000 species
Scaphopoda <http://en.wikipedia.org/wiki/Scaphopoda>  - tusk shells; 350
species
Gastropoda <http://en.wikipedia.org/wiki/Gastropoda>  (Univalves) - sea
snails with shells, such as abalone <http://en.wikipedia.org/wiki/Abalone> ,
limpets <http://en.wikipedia.org/wiki/Limpet> , conch
<http://en.wikipedia.org/wiki/Conch> , etc, and marine snails without a
shell or with a reduced shell, such as nudibranchs
<http://en.wikipedia.org/wiki/Nudibranch> , sea hares
<http://en.wikipedia.org/wiki/Sea_hare> ; sea angel
<http://en.wikipedia.org/wiki/Sea_angel> , sea butterfly
<http://en.wikipedia.org/wiki/Sea_butterfly> , sea lemon
<http://en.wikipedia.org/wiki/Sea_lemon>  etc; land snails
<http://en.wikipedia.org/wiki/Snail>  and slugs
<http://en.wikipedia.org/wiki/Slug> , freshwater snails, total estimated at
40,000 - 150,000 species
Cephalopoda <http://en.wikipedia.org/wiki/Cephalopod>  - squid
<http://en.wikipedia.org/wiki/Squid> , octopodes
<http://en.wikipedia.org/wiki/Octopus> , nautilus
<http://en.wikipedia.org/wiki/Nautilus> , cuttlefish
<http://en.wikipedia.org/wiki/Cuttlefish> ; 786 species, all marine

The ability to distinguish all these species of Molluscs is a considerable
problem for Malacologists.  It is less of a problem for shell collectors who
generally focus on bivalves and univalves.  And, within these two groups
most collectors focus upon only the marine species of the larger,
hard-shelled specimens and eschew micro shells (< 10 mm).  However, this
limited group still includes scores of thousands of described and
undescribed species and represents a formidable challenge for collectors.

The identification and classification (taxonomy) of living organisms is
probably among the oldest of human penchants.  The version of taxonomy we
practice is the binomial naming and hierarchical classification system
introduced by Carolus Linnaeus in the mid-18th century.  This system has
largely been based upon observers' differing opinions of what are valid
morphological characters to serve as distinctions between species, the
significance of such characters as distinguishers, and the observers'
attitudes toward observational and research rigor when establishing species
distinctions.  So, on the one hand we have a very large number of described
species (the accuracy of which has been limited by the observational,
research and reporting skills of taxonomists who created past species
distinctions) and on the other hand we have the challenge of our own
capacity for morphological examination, ability to recall the names and
diagnostic morphological features of species, and/or research resources to
accomplish comprehensive and valid comparative analysis.  Learning the
morphological nuances that separate closely allied species is so complex
that few professional malacologists, even those who have devoted their
careers to taxonomy, can critically discriminate more than 1,000 species.
The consequence is that routine, accurate identification of more than
several hundred described shell species is an acute challenge for most
malacologists and especially collectors, with a delay typically measured in
months to acquire identities for even a short list of specimens - assuming
that a qualified expert can be found.  How much easier it would be for us
all if every shell had a little code on it identifying its true name.  CBOL
is coming.


Marlo
merritt island, fl

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