What means “crabbed” shell ?

(Original Forum Question : Hi, Just what does it mean when a dealer says a specimen was collected crabbed. What type of damage should one expect to find on such a shell. Thanks.)

"Crabbed" means that the original owner of the shell (the gastropod) had died and decomposed, and a hermit crab had moved into the empty shell. Hermit crabs are fairly fussy about shell size (they have to be – their life depends on it!) but they are not very fussy about shell quality. Therefore a "crabbed" shell can range from near gem condition to really awful condition. The crab actually does help to preserve the shell in the condition in which it "collected" it, because the crab supports the shell on its back and prevents the shell from being rolled around by the waves and currents as it would if empty.
(Answer by M. Paul Monfils via the Forum)