A holotype can get a bit more complicated if the original author based the description on multiple specimens.  Ideally, a single specimen would have been picked out as the holotype, in case later study revealed that more than one species was present in the original set of specimens.  (I believe that this is now required for describing species, but do not have the information handy.)  However, sometimes there is confusion about the identity of the holotype.  For example, the original specimen may be damaged or lost, or perhaps the author failed to designate a unique holotype and later study reveals multiple possibilities.

Conversely, sometimes the holotype is avilable and recognizable but overlooked in the corner of some museum.  Especially if the original description was not too clear, the name may be misused until someone discovers the mistake.  The most extreme example of this that I know of is a genus and species, purportedly a dinosaur, that turns out to have as holotype a chunk of petrified wood.  However, this is an issue for mollusks as well.  The common eastern Pacific Argopecten was recently recognized as A. ventricosus rather than A. circularis when study of the holotype of circularis showed that it was actually a specimen of the Western Atlantic A. irradians.  Even more confusing is the case of a couple of Dall's Eocene taxa from the southeastern U.S.  Eucymba ocalana and a similarly named cassid were described and figured based on molds from the Ocala Limestone (hence the species name).  However, he later designated other specimens, not from the Ocala Limestone, as holotypes.  These specimens are possibly not even congeneric with the figured and discussed specimens.  Eucymba ocalana is the type of Eucymba, so both the genus and the species are confused.

    Dr. David Campbell
    "Old Seashells"
    Biology Department
    Saint Mary's College of Maryland
    18952 E. Fisher Road
    St. Mary's City, MD  20686-3001 USA
    [log in to unmask], 301 862-0372 Fax: 301 862-0996
"Mollusks murmured 'Morning!'.  And salmon chanted 'Evening!'."-Frank Muir, Oh My Word!