For those of you who enjoy knotty taxonomic problems like the ones mentioned here, or want to pursue it further, try:

Taxonomy, by George Gaylord Simpson.  Old, but a very nice summary of how animals are named.

The Academy of Natural Sciences of Phildadelphia published a catalog of their vertebrate fossils a couple of years back.  Although not shell related, it has a wonderful discussion about how one tracks down the history of a species name or genus name, and is worth reading by anyone interested in the practice of Taxonomy.