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Arquivos de Zoologia

Nuttal (1990: 260), including the lectopype, are apparently of young specimens, which explains the specific name.

Genus Melanoides 01iver, 1804 (Type species: M. fasciolata 01iver, 1804 = Thiara tuberculata Muller, 1774)

Melanoides tubercuiatus (Muller, 1774)

(Figs 9,10,46,47, 54, 55, 87, 169-188)

Synonymyc list see Starmiihler (1969: 224) and Brandt (1974: 164-165). Complement: Thiara {Melanoides) tuberculata: Abbott, 1948: 289-290 + pl. 3, fig. 13.

Melanoides tubercuiatus: Starobogatov & Izzatullaev, 1980: 31, figs 5, 11.

Melanoides tuberculata: Houbrick, 1987a: 44; OHveira et al., 1981:97.

NB.: according to Stone et al. (1965) the genera with the sufifbc -oides are masculine in gender, thus "tubercuiatus ” is morę appropriate than "tuberculata

Description.

Shell (figs 9, 10, 46, 47). Medium sized (up to 30 mm), turriform, narrow, apex generally present. Protoconch of two smooth whorls; junction of protoconch and teleoconch not elear; gradually several spiral and axial ribs appear, both predominating, giving a reticulate effect (fig. 46), spiral ribs somewhat tali. Periostracum heavy, brown. Sculpture spiral ridges of somewhat uniform width, about 10 in penultimate whorl; a somewhat broad, shallow furrow between; axial ribs close with each other (about 18 in penultimate whorl), spiral ridges runs on axial ribs (fig. 47). Ostracum pale beige with sparse axial dark brown bands. Aperture elliptical without elear canal. Other details in Brandt (1974: 165-166, pl. 12, figs. 9-12).

Head-foot (figs 169-171,173). Color dark brown, coalescent spots in anterior region of head and dorsal regions of foot. Snout broad, dorso-ventrally flattened, anterior margin bilobed. Tentacles with about same length than snout. Eyes dark, near tentacle’s base, without ommatophore. Brood pouch described below. Other head-foot structures similar to those of preceding species.

Operculum (figs 54, 55). Dark, elliptical, nucleus sub-terminal; occupies entire aperture. Inner scar elliptical, near inner margin.

Mantle organs (figs 172, 174-176). Mantle border with some lobed tentacles, different in size and well spaced one another. One or two tentacles in right extremity and three or four in left extremity morę developed. Osphradium ridge-like, with about half of gili length, situated posterior to gili beginning. Space between gili and rectum proportionally narrow. Rectum large, broad, with fecal pellets oblique, compacted. Anus siphoned. Pallial oviduct described below.

Excretory and circulatory Systems (figs 174, 176). Heart as described for preceding species. Kidney proportionally large, about a third whorl in length, with two lobes. Both lobes hollow, with a series of transversal septa, inserted in a longitu-dinal vessel. A thin transversal membranę between both lobes; other membranę between posterior (visceral) lobe and pericardial cavity. Anterior (pallial) lobe with radial septa and glandular tissue morę developed. Nephrostome in right-posterior extremity of membranę between kidney and pallial cavity, close to rectum.

Digestive system (figs 177-181, 183-188). Very similar to those described for preceding species. Distinctive and interesting features follow. Two pair of folds in inner surface of dorsal wali of buccal mass, posterior to jaws, with two pairs of dark spots laterally (fig. 179); m4 and m5 insertion connected one with other; m5 connected with its pair in distal region near they insertion (figs 184-188); pair of ml 1 with insertion in anterior region of cartilages, in ventral region of peri-buccal muscles and in m7. Radula short, “S”-shaped. (figs 187,188). Radula (fig. 87): similar to Aylacostoma preceding species, rachidian tooth with 7 cusps; lateral tooth with 5 cusps, second cusp larger; mar-ginal teeth with 5 cusps. Esophagus without crops nor glands, intemally three narrow folds. Stornach (figs 177, 178) with relatively large dorsal-left sorting area divided into 2 regions: anterior and lateral-left (this larger); lateral-left region lied at right by two folds, that anterior broader and shorter than that posterior (fig. 178: gf). Central pad long, with central, longitudinal, shallow furrow, curved to right posteriorly. Crescentic ridge absent or fiised with posterior region of central pad (fig. 177: cr). Intestine aperture preceded by only one fold,