Colonial metazoans that lived symbiotically with hermit-crabs create striking and distinctive fossils. Examples of such fossils recorded (Schindler and Portell, 1993) from Cenozoic deposits in Florida include the scleractinian coral Septastrea marylandica (Conrad, 1841) (see Darrell and Taylor, 1989), the hydrozoan Cystactinia ocalana Brooks, 1964, and the bryozoan Hippoporidra edax (Busk, 1859) recorded as H. calcarea (Smitt) by Scolaro, 1970. In all of these fossils, the symbiotic colony covers the entire external surface of a gastropod shell with a thick encrustation. Growth of the colony outwards from the shell aperture in the form of a helicospiral tube greatly extends the size of the chamber available for the hermit-crab occupant. In no known fossil examples of symbioses are the hermit-crabs preserved in situ. However, modern analogues, along with functional morphological considerations, provide good criteria for inferring that this peculiar colonial growth pattern occurred in response to the presence of a symbiotic hermit-crab, at least for examples within the Lower Jurassic-Recent range known for fossil hermit-crabs (see Walker, 1992; Taylor, 1994).