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Arquivos de Zoologia

Spermoduct relatively broad, color white, walls thick, running close to columella. In right region of pallial cavity, beside rectum, becomes an open groove with thick glandular walls (prostatę).

Female. Pallial oviduct very large (when developed), described by Marcus & Marcus (l 963-. 89, fig 87), with 2 receptacles in inner lamina and one bursa in outer lamina. Ovopositor (fig. 333) a large flap in dorsal right region of fool, with a lon-gitudinal middle furrow originated from pallial cavity right floor, and becoming deeper anteriorly. Other details of genital system in Marcus & Marcus (1963: 87-91).

Measurements (in mm). 5.2 by 2.1; 4.3 by 1.8 (figured specimens).

Distribution. From North Carolina, USA, to Rio Grandę do Sul, Brazil.

Habitat: Generally moving on algae, intertidal and infratidal levels. Sometimes are found crawling on rocks and corals.

Materiał examined. Brazil; Rio de Janeiro; Angra dos Reis, Leste Beach, 60 specimens, MZSP 25146 (18/vii/1966); Sao Paulo; Ubatuba, Andori-nhas Beach, 6 specimens, MZSP 28251 (22/i/1963); Sao Sebastiao, Barequeęaba beach, 6 specimens observed alive, MZSP 28613 (16/v/1997, Simone col.); Guaeca beach, 4 specimens observed alive, MZSP 28635 (17/v/l 997, Simone col.).

Family Diastomatidae Genus Finella A. Adams, 1869 (Type species: C. pupoides A. Adams, 1860)

Finella dubia (Orbigny, 1842)

(Figs 29,30,49,65,66, 104, 105, 345-361)

Chemnitzia dubia Orbigny (in Sagra), 1842: 226 (pl. 17, figs 4-6); 1846: 398.

Bittium (?) yucatecanum Dali, 1881: 90.

A laba cerithiidioides Dali, I889a: 258.

Bittium (Alabina) cerithioides: Morretes, 1949:79. Alabina cerithiideoides: Warmke & Abbott, 1961: 73 (pl. 13, fig. b).

Finella dubia: Abbott, 1974:108 (fig. 1039); Rios, 1975: 49 (pl. 13, f. 182); 1985: 52 (pl. 19, f. 230); Jong & Coomans, 1988:45 (pl. 15, fig. 213); Rios, 1994: 63 (pl. 21, f. 241).

Description.

Shell (figs 29,30,49). Smali (up to 10 mm), slender, tuniform, up to 9 whorls. Color generally pale beige with brown apex; sometimes entirely brown. Sculpture thin axial regular ridges; in first whorls spiral sculpture also present, but morę insipid than axial ones, gradually faint; some specimens with a stronger spiral ridge in periphery of fiist whorls, almost a carina, with nodes in intersection with axial ridges. Strong and broad axial thread sometimes present, rarely up to three per specimen. Periostracum opaque, yellowish, transparent. When decalcified, inner chitinous layer present, pale brown, transparent (fig. 348: ic). Aperture simple, elliptical, canal weak.

Head-foot (figs 345, 346, 350). Pigmented by dark brown spots in head, tentacles and lateral region of foot; most part pale beige. Head protniding. Snout sub-cylindrical, relatively smali (about half of tentacles length), bilobed anterior margin. Tentacles long, with dark eyes near they base without ommatophore. Foot large, without visible divisions except a shallow furrow between sole and dorsal regions; an evident anterior flap (j 1), in its border a furrow of pedał glands. A deep longitudinal furrow in posterior half of sole. No ovopositor developed. Columellar muscle of about

1.5    whorls.

Operculum (figs 65,66). Similar to that of B. varium.

Pallial organs (figs 347, 348, 351). Mantle border flanged by short, broad, flattened papillae, narrower in siphon region. Pallial cavity of about

1.5    whorls. Osphradium long, discretely shorter than gili; ridge-like, with some sparse constrictions; brown pigmented. Satellite fold around osphradium, broad in its anterior half, gradually narrows in both sides in posterior half, which have about same osphradium length; color white. Gili somewhat long, begins at some distance from mantle border, filaments rectangular and Iow. Between gili and rectum a relatively broad space when genital ducts run. Rectum narrow, near right margin of cavity (but not in extremity), dorsal to genital ducts, bears fecal pellets somewhat spherical, not obliquely compacted. Anus siphoned, posterior from mantle border.

Circulatory and excretory Systems (figs 350, 351). Very similar to those described by B. varium.