There was a tibia found many years back that was named "serrata" or
something like that. it looked much like a tibia insulaechorab (Roding 1798)
but the serration ran all the way from the posterior end to the spire tip in
one un-broken line much like a steak knife. whether this was a "rare" shell
or just a mutation is unknown as the one shell found has never surfaced
since it was discovered.
 
Mark James & Peta Susan Bethke
3001 South Ocean Dr. Suite 4-V
Hollywood, Florida
33019-2804
U.S.A.