Paleonet: Cinctura rhomboidea (Rogers and Rogers 1837)

[Allen Aigen]

I am slowly updating and expanding a study of Fasciolaria and Cinctura species, living and fossil, from Brazil to North Carolina.  C. rhomboidea (as described from the Yorktown Formation of Virginia) is fairly small and broad and lacks protoconch sculpture.  I know that it occurs as elongate narrow specimens from the Duplin, also lacking protoconch ribs.   In the Pinecrest Beds (Petuch Unit 7, possibly others)  of southern Florida (Late Pliocene) there appears to be mostly larger, elongate, narrow specimens,  but the protoconch is usually not well enough preserved to be certain that it is smooth.  Many (but apparently not all) have axial protoconch ribs, which is typical for C. apicina (Dall) which was named from the succeeding (Pleistocene) Caloosahatchee Formation.  C. apicina generally is shorter and broader than C. rhomboidea, but I do not know if that is consistent enough to separate the species, regardless of the protoconch. Complicating the problem is C. sarasotaensis (Petuch, 1994) found in the Pinecrest (Petuch Unit 4), which has clear protoconch ribs but is shorter and broader than either of the common species (an apparent ecological variety?) .  
If anyone has information or access to specimens of C. rhomboidea that may add useful information to this problem, I would be very happy to hear from you!    .  
Thanks,Allen Aigenserirach at ymail.com
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