identify types of conch shells, some very old

[paul monfils]

The first row, from their appearance and your description, appear to be fossils. Perhaps Strombus floridanus, though I don't know much about fossils.
The second row appears to be two Strombus pugilis and one Strombus lentiginosus. The latter shell is the only one in the photograph that is not from Florida/Caribbean.
The third row, badly worn but probably Strombus raninus.
Fourth row, very worn, could be S. pugilis, or perhaps a fossil predecessor of S. pugilis.