. Bulletin. Science; Natural history; Natural history. . 1mm . 1mm Fig. 3. Hipothoa hyalina (L). A multilaminar portion of the colony. Fig. 4. Membranipora arborescens (Canu & Bassler). Opesial membrane is removed, showing thick cryptocyst with small spines, and fused block-like tubercles. the frontal wall, and a brown line generally separating the zooids. The gulf coast colonies of Membranipora arborescens that were encrusted on hermit crab oc- cupied shells in this study were pleurilaminar, never arborescent, had small cryp- tocystal denticles and chitinous spinules, and the brown line s
. Bulletin. Science; Natural history; Natural history. . 1mm . 1mm Fig. 3. Hipothoa hyalina (L). A multilaminar portion of the colony. Fig. 4. Membranipora arborescens (Canu & Bassler). Opesial membrane is removed, showing thick cryptocyst with small spines, and fused block-like tubercles. the frontal wall, and a brown line generally separating the zooids. The gulf coast colonies of Membranipora arborescens that were encrusted on hermit crab oc- cupied shells in this study were pleurilaminar, never arborescent, had small cryp- tocystal denticles and chitinous spinules, and the brown line separating the zooids was irregularly present. The cryptocyst was thick, fused, and block-like tubercles were present. A few kenozooids were produced where growing edges meet, and sheets of zooids were large and regular. Occasionally the shell surface was etched. Bryozoan Encrusting Patterns Gulf Coast, Recent.—The initial sites of encrustation by the bryozoans are oriented in relation to the position of the crab in the shell. On the shells from the Gulf of Mexico (Fig. 5), the inner surface of the outer lip of the gastropod shell was above the anterior end of the crab and the inner lip (base of the columella) was below the anterior end (See Carleton and Roth 1975, for terminology). These two areas are usually colonized initially; subsequently colonies expand outward and over the gastropod shell surface (Fig. 6A, B). Analysis of colony edges indicates that fusion may take place, due either to recognition of sibling colonies or to fusing of single colony segments after growing apart (Chaney 1983). There were also scattered indications of redirected growth between nonsibling zooids (Chaney 1983). The data on the bryozoan encrusting sites are listed in Table 2. California, Recent.—The hermit crab Pagurus samuelis occupies Tegula fu- nebralis shells. Initial points of bryozoan encrustation are above and/or below the anterior end of the crab, as indicated by the cheliped in Fig.
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