Trypostega striatula (Smitt, 1873)

(Fig. 22; Table 21)

Gemellipora glabra f. striatula Smitt, 1873: 37, pl. 11, fig. 207 (not figs 208–210).

Lepralia inornata: Smitt 1873: 61, pl. 11, figs 215–216.

Trypostega venusta: Osburn 1914: 198; 1940: 409; 1947: 28; Canu & Bassler 1920: 330, pl. 85, figs 15, 16; 1928a: 77, pl. 8, figs 15, 16; Marcus 1938: 35, pl. 8, fig. 19; Shier 1964: 627; Cook 1968: 184; 1985: 141; Lagaiij 1973: 147, pl. 2, fig. 10; Winston 1982: 151, fig. 86; 1984: 18, figs. 37, 38; Taylor & Foster 1994: 8, pl. 3, figs 1–4.

Trypostega striatula: Winston 2005: 39, figs 101–103.

Material examined. VMNH no. 70633, 70634; USNM no. 1283248.

Description. Colonies encrusting, unilaminar, with flat, porcellanous gymnocystal frontal walls (Fig. 22 A). In SEM images faint wavy striations visible on frontal-wall surfaces. Autozooids rhomboidal, with shallow, regularly spaced pores, and small suborificial umbo (Fig. 22 B). Autozooid orifices cleithridiate, anter rounded, with sharp downward projecting condyles, and V-shaped sinus (Fig. 22 D). Colonies polymorphic; small heterozooids (zooeciules) with frontal-wall structure like that of autozooids found at distal ends of autozooids and may occur irregularly in other locations. Zooeciules with small elliptical orifice at raised distal end, slightly narrowed laterally, but without distinct condyles (Fig. 22 E, F) Ooecia large, flattened, embedded in frontal calcification, with numerous small, evenly spaced pores like those in autozooids, and with central longitudinal ridge (Fig. 22 E, F). Embryos reddish orange.

Remarks. Trypostega striatula autozooids are more elongate with a slightly larger number of gymnocystal pores and slightly deeper, more curving V-shaped sinuses than the similar European T. venusta. The most significant morphological difference is in the shape of female zooidal orifices, which are similar to those of autozooids in T. striatula, but broader and shallower in T. venusta. Zooeciules are thought to be male zooids, but they may also be space-fillers, as they also occur patchily as space fillers on colony surfaces where there has been injury and regeneration. Those that appear in response to injury tend to be larger and more irregularly polygonal than those that develop in regular series.

Distribution. Cape Hatteras to Brazil. Caribbean, Gulf of Mexico.