(Figs 6–9, Table 2)
Material examined. Holotype: UFBA 336, Praia de Guarajuba, Camaçari, Bahia State, Brazil (12 º 50 ' S, 38 º 10 ' W), 28 m, sand, collected March 2002 by W. Andrade. Paratypes: UFBA 339, Ilha de Trindade, Espírito Santo State, Brazil (20 º 30 ' S, 37 º 18 ' W), 93 m, collected April 1996 by REVIZEE Expedition, 93 m; UFBA 477, Camamu, Bahia State, Brazil (13 º 45 ' S, 38 º 45 ' W), 47 m, collected December 2006 by W. Andrade; UFBA 499, Camamu, Bahia State, Brazil (13 º 45 ' S, 38 º 50 ' W), collected August 2004 by W. Andrade; UFBA 500, Itacaré, Camamu, Bahia State, Brazil (14 °02' S, 38 ° 52 ' W), collected August 2004 by W. Andrade. Additional material: UFBA 333, Praia de Guarajuba, Camaçari, Bahia State, Brazil (12 º 50 ' S, 38 º09' W), 37 m, gravel, collected March 2002 by W. Andrade; UFBA 337, Praia de Arembepe, Camaçari, Bahia State, Brazil (12 º 44 ' S, 38 º04' W), 28 m, gravel, collected March 2002 by W. Andrade; UFBA 496; Praia de Guarajuba, Camaçari, Bahia State, Brazil (12 º 50 ' S, 38 º 11 ' W), 23 m, gravel, collected September 2002 by W. Andrade; UFBA 502, Praia de Guarajuba, Camaçari, Bahia State, Brazil (12 º 50 ' S, 38 º09' W), 23 m, gravel, collected September 2002 by W. Andrade; UFBA 507, Camamu, Bahia State, Brazil (13 º 47 ' S, 38 º 52 ' W), 23,5 m, gravel, collected December 2006; UFBA 515, Praia de Arembepe, Camaçari, Bahia State, Brazil (12 º 45 ' S, 38 º07' W), 22 m, gravel, collected March 2005 by W. Andrade; UFBA 525, Praia de Guarajuba, Camaçari, Bahia State, Brazil (12 º 52 ' S, 38 º 10 ' W), 45 m, sand, collected February 2006 by W. Andrade; UFBA 526, Camamu, Bahia State, Brazil (13 º 46 ' S, 38 º 52 ' W), 24,7 m, gravel, collected December 2006; UFBA 585 Praia de Guarajuba, Camaçari, Bahia State, Brazil (12 º 51 ' S, 38 º 12 ' W), 23 m, gravel, collected September 2007 by W. Andrade.
Diagnosis. Colony white, vitreous, multilaminar, encrusting varied substrata. Zooids convex, orifice hoofshaped with a pair of lateral condyles and a broad shallow poster. Ooecium with large frontal slit.
Etymology. Latim fissura, slit, alluding to the frontal surface of the ooecium.
Lz lz Lo lo Lav lav Lov lov MIN. 0.366 0.272 0.103 0.103 0.055 0.044 0.134 0.162 MAX. 0.501 0.465 0.145 0.152 0.090 0.065 0.198 0.255 MEAN 0.420 0.367 0.130 0.123 0.076 0.054 0.168 0.215 STD DEV. 0.035 0.055 0.015 0.014 0.009 0.005 0.019 0.026 Description. Colony white, vitreous, encrusting nodules, shells, and dead bryozoan colonies on a substratum of sand to gravel. Uni- to multilaminar, forming small nodules to large colonies obscuring the substratum. First layer with zooids regularly orientated, subsequent layers with irregular orientation. Zooids convex, rhomboidal, hexagonal, with small marginal pores. Frontal shield thickly calcified, sometimes with small frontal pores. Orifice large, hoof-shaped with a pair of lateral condyles slightly down-curved, poster broad and shallow. Acute triangular avicularium often present, with complete cross-bar frequently laterally directed; sometimes absent in entire colonies. Ooecium hyperstomial, globose, not closed by operculum, with large frontal slit.
Remarks. Although Winston (2005) pointed out that additional species could be placed in Hippotrema, the only species recognized so far is the type species. Hippotrema fissurata n. sp. differs from H. janthina mainly in having a fissured ooecium; H. janthina merely has a less-calcified frontal area (Cheetham & Sandberg 1964; Winston 2005). Additionally, Besides, H. fissurata n. sp. is white, vitreous and exclusively encrusting whereas H. janthina is deep purple or blue-black (Osburn 1914) and can become branching (Winston 2005). The two species also differ in the autozooidal and avicularian metrics—the zooid is broader in H. fissurata than in H. janthina (0.272–0.465 mm vs 0.28–0.30 mm), while the avicularium is broader in H. janthina (0.06 – 0.06 mm vs 0.044– 0.065 mm). The avicularium is common in H. janthina (Winston 2005) but in H. fissurata it can be lacking in entire colonies.
Characodoma rotundorum (Norman, 1909) possibly belongs to Hippotrema (Winston 2005), but differs from H. fissurata in having a heavily calcified frontal wall and ooecium with a large uncalcified frontal area (Cook 1985). Winston (2005) also suggested that Characodoma latisinuatum Harmer, 1957 might also belong to Hippotrema. It differs from H. fissurata in its erect growth and densely pseudoporous and minutely tubercular frontal shield (Harmer 1957; Cook & Bock 1996). Both Characodoma latisinuatum and Hippotrema fissurata n. sp. have a large frontal ooecial fissure but the ooecia may be obscured by secondary calcification in C. latisinuatum (Cook & Bock 1996).
Distribution. Brazil: States of Bahia and Espírito Santo, 22–93 m depth.