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). Schindler and Portell (1993) reported a cheilostome referred to the genus Aimulosia from the Eocene Crystal River Formation (currently defined as the Upper Ocala Limestone, e.g., Oyen and Portell, 2001) as the oldest Florida example of a bryozoan that lived symbiotically with hermit-crabs. Subsequent research on this bryozoan has shown that it is an undescribed species belonging to another cheilostome genus, Hippoporidra Canu and Bassler, 1927. These new findings add to the significance of the Ocala Limestone fossil, here formally described as H. portelli n. sp., because it now becomes the oldest known example of the most widespread bryozoan genus that lives almost entirely symbiotically with hermit-crabs, extending the first appearance of the genus Hippoporidra back in time from the Early Miocene (Burdigalian) to the Late …