The difficulty of identifying species in this interval and region is
exacerbated by the high variability in many lineages.  Both sinistral
Busycon and Conus appear in this interval.  Several species show odd
variation in Virginia during this time, and the number of variable forms
increases as you go south through the Carolinas into Florida.  For example,
Mercenaria has the full range of variability in Virginia (tridacnoides
form, etc.).  Glycymeris americana occasionally has the quinquerugata form
in Virginia and very rarely abberrans.  These are more common further
south.  Chesapecten septenarius is uniform in Virginia, but has wild
variation in rib number in the lower Pliocene of South Carolina, along with
high variability in Nodipecten peedeensis, not found to the north.  The
Macrocallista albaria/reposta/greeni/nimbosa lineage seems to gradually
evolve in the Carolinas and Virginia, but shows wide variation in Florida,
as does Siphocypraea.  Thus, the Floridian faunas have an extremely high
variability.  Naming forms without consideration of a large suite of
specimens is especially doubtful under these circumstances.


Dr. David Campbell
"Old Seashells"
Department of Geological Sciences
CB 3315 Mitchell Hall
University of North Carolina at Chapel Hill
Chapel Hill NC 27599-3315 USA
[log in to unmask], 919-962-0685, FAX 919-966-4519

"He had discovered an unknown bivalve, forming a new genus"-E. A. Poe, The
Gold Bug