Dear Art,
 
Species names are composed by two words (two nouns = binomen),
following a very common and incredibly simple rule devised by Linne
during the second half of the 18th century. It is a common and simple
rule indeed because its rationale did not differ too much of how
people used to refer to organisms. That is, (a) giving the organism a
generic name plus (b), a qualifier of such name (adjective, epithet,
etc.), in order to make the critter distinguishable from others. We
still do this, and we just have to check the common names of our
favorite shells to realize it. Please, allow me to get into this
simple example, where only two names are used:
 
"Queen Conch" is composed by two nouns:
 
(a) "Conch", that represents the generic name of this kind of snails
(b) "Queen", an epithet that refers to a quality of "Conch"
 
Notice that "Queen", in this case is also a name, but in the combined
word "Queen Conch", it refers to a quality of this snail ("this Conch
is the Queen of all Conchs") Then, the name "Queen" behaves as an
epithet.
 
Now, during the 18th century the most used scientific language was
Latin, with a lot of influence from Greek. Then, the ruling of
putting together two words for referring to an organism (and only two
words: a noun and a qualifier), had to comply with some rules of the
Latin language. Analogously to the example above (and it does not
imply necessarily any cause-consequence relationship), species get
"Latinized" binominal names as the one in your example: _E. =
Epitonium? rariforme_
 
_Epitonium rariforme_: this name identifies this particular organism
at the rank of species. It is therefore what we call the "Species
Name". As the ICZN indicates, it refers to a taxon and it is composed
by two words:
 
_Epitonium_, that plays the role of  the "generic name" of the group
to which the critter belongs. We call this part of the species name
"Genus", and it represents a whole taxonomic category by itself.
 
_rariforme_, that is the "Specific Epithet" or "Specific Name" that
modifies or defines a quality of the Genus (noun) _Epitonium_, for
this particular organism.
 
So, we have a nice snail called "the rare-shaped _Epitonium_." In
other words, among all snails of the _Epitonium_ group, we call this
particular species the rare-shaped _Epitonium_ , and therefore, it is
for us different from the rest of the _Epitonium_ snails.
 
Notice that the epithet rare-shaped (_rariforme_) by itself (alone),
does not tell us anything about any taxon in particular (as the ICZN
wisely advises). If we are able to understand the specific epithets
as what they really are (just epithets), then it is easy to realize
that if they do not come together the name they modify (in this case,
the Genus name), they cannot make too much sense by themselves:
 
(a) either for the purposes of the identification of the organism, or
(b) on the basis of the definition of epithet according to (some of)
our languages.
 
These are probably some of the (very) basic "rationales" that explain
why species names are ruled to be a binomen.
 
But time goes on (approx. 240 years). The inherent simplicity of the
binominal nomenclature eventually became a very complicated matter.
The wording, technicalities, ruling, etc. and other very needed
"complexities" increased as a consequence of the expansion of the
method (application to many more organisms + many more people using
it), and as a product of its updating with the growing of the
biological knowledge.
 
As any other human enterprise, the binominal nomenclature system is
by no means perfect, and it is full of exceptions. Nevertheless, I
think that it is a very useful tool and right now, it is the best we
have on hand.
 
Art, I hope this helps to clarify your question, as well as my point.
 
Cheers,
 
Rob
 
|
| Rob;
|    That's not much help. I know what an epithet is. I also know
what
| an epigram and an epitonium are. What we need to know is how the
| "epithet" differs from the species name. For instance: E. rariforme
| is both the species name and a good description of the critter
being
| rare. What's the difference?
|                Art