Bruce Neville wrote,
>1.  I just happened to be looking at Petuch's "Atlas of Florida Shells"
>the other night and noticed the comment, "Along with C. heilprini, C.
>mitchellorum was probably the last-living left-handed cone"(p. 361).
>Unfortunately, he does not give stratigraphic details beyond "Pliocene
>and Pleistocene" in the subtitle of the Atlas.
 
The age assignments in current literature are not always correct.  The
upper Calossahatchie and Waccamaw Formations are uppermost Pliocene to very
basal Pleistocene, but are often referred to the Pleistocene.  (Not to
mention that some authors, mostly in northern Europe, are trying to change
the Pliocene-Pleistocene boundary from 1.6 to 2.5 million).  Likewise, the
Yorktown, Duplin, Raysor, and Pinecrest Formations are no younger than
about 3.5 million and mostly before 3.8 million.
 
 
>While I don't agree with a lot of Petuch's species, and he has surely
>over-split the subgenus Contraconus, as well, I cannot believe from his
>plates that they are _all_ adversarius.
 
It shows extremely high variability, and intergrades exist between many of
his forms, if not all.
 
 
David Campbell
 
"Old Seashells"
 
Department of Geosciences
CB 3315 Mitchell Hall
University of North Carolina at Chapel Hill
Chapel Hill NC 27599-3315
USA
 
919-962-0685
FAX 919-966-4519
 
"He had discovered an unknown bivalve, forming a new genus"-E. A. Poe, The
Gold Bug