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after free ftom style sac, bears two loops in right side of this, in this region, intestine with dark spots. Intestine free from kidney tissue. Rectum and anus see pallia! cavity. Digestive gland restricts to poste-rior region of stornach, and with about three whorls posterior to it.

Genital system. Gonad occupies superior regions of each whorl, on digestive gland. Małe (fig. 384). Spermoduct a narrow duet close to columella; in right posterior region of pallial cavity expands, becomes a long, thick glandular funow, without special inner structures except a fold in inner lamina; fmishes posterior to anus. Female (fig. 383). Oviduct also close to columella, in right posterior region of pallial cavity expands but maintains closed at about 1/8 of its length in pallial cavity; afterwards opens, becoming a thick glandular groove. Both laminae present a posterior chamber each, blind sacs opened anteriorly in furrows which nins just in lamina borders; in inner lamina a bursa copulatrix, and in outer lamina a seminal receptacle, this smaller than bursa. Pallial oviduct fmishes posterior to anus. Gonopericardial duet or ligament present in both sexes, smali. No ovopositor differentiable.

Measurements (in mm). 13.4 by 5.0; 13.1 by5.0; 12.5 by 4.3; 13.2by 5.6(figuredspecimens).

Distribution. FromFlorida, USA, to Rio de Janeiro, B raził.

Habitat. Estuarine environment, moving on mud or on root trees.

Materiał examined. Venezuela; Nova Esparta; Margarita Island, Porlamar city, Caracola estuary, 150 specimens, MZSP 28262 (30/i/1996, Simone col.).

Remarks. B. minima differs in its digestive system from Califomian B. zonalis (Bmg.) (cf. Driscoll, 1972) in having longer stornach and central pad morę developed.

Family Cerithideidae

Genus Cerithidea Swainson, 1840 (Type species: Mumx decollata Linne, 1758)

Cerithidea costata (da Costa, 1778)

(Figs 40, 41, 50, 70, 71, 109, 110, 390-405)

Synonymy: see Beąuaert, 1942: 2. Complement: Cerithidea costata: Warmke & Abbott, 1961: 71

(pl. 13, fig. s); Abbott, 1974: 102 (fig. 980);

Jong & Coomans, 1988: 43 (pl. 33, fig. 203).

Description.

Shell (figs 40, 41, 50). Most specimens covered by a brown mass of vegetal fibers, with about double of width and length than shell, only aperture free (fig. 40). Protoconch of two whorls smooth, convex, generally eroded (fig. 50). Other details in Beąuaert (1942: 2-3, pl. 1, fig. 1; pl. 2, figs 1-7).

Head-Foot (figs 390-392). Pigmented by uniform bluish gray in dorsal region of foot and head, and transversal violet-brown bands in snout and sometimes in tentacles; foot sole white; sometimes tentacles entirely violet-brown; posterior regions pale beige. Head protruding. Snout large, dorso-ventrally flattened, bilobed anterior margin. Tentacles long, stubby, with dark eyes approximately in its middle region; region from tentacles base to eye clearly broader than distal region. No ommatophore. Foot of medium size, without divisions; a furrow in anterior margin of pedał glands. Columellar muscle of about 1.5 whorls.

Operculum (figs 70,71). Circular, comeus, nucleus central, multispiral. Edge fimbriated. Occupies entire aperture. Muscle scar elliptic, near inner margin.

Mantle organs (figs 393-396). Mantle border almost smooth, some specimens with 5 to 7 smali papillae sparsely disposed. Pallial eye well-developed, dark, with lens, situated in a smali elevation in left region, just in incurrent canal. Mantle cavity rather deep, about two whorls. Osphradium very long, ridge-like, lying left margin of pallial cavity, close gili, little less than half of gili length; osphradium anterior extremity posterior than that of gili. Gili long, about same length than pallial cavity; filaments triangular, tali, tip almost central; sharp anterior extremity near mantle border. Ctenidial vein of medium size. Between gili and rectum a proportionally narrow area. Hypobranchial gland inconspicuous. Rectum broad, covered by ad-rectal sinus, intemally several elliptical fecal pellets compacted obliąuely. Anus siphoned, posterior to right extrcmity of mantle border. Pallial gonoducts run between rectum and right margin of cavity, narrow, long, finish posterior to anus.

Circulatory and excretory Systems (figs 395, 396). Heart large, pericardium also large, exposed