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178

Arquivos de Zoologia

13, fig. v); Rios, 1970:42; Abbott, 1974:103 (fig. 990); Rios, 1975: 52 (pl. 14, f. 195); Abbott & Dance, 1983: 63 (fig.); Rios, 1985. 49 (pl. 19, f. 219); Jong & Coomans, 1988:44 (pl. 33, fig. 206); Rios, 1994:64 (pl. 21, f. 244).

Description.

Shell. The high degree of shell variation and anomalies is a character of this species, as also noted Abbott (1974:103). Some samples are found in figs 32-39. Color varies from pale cream to dark brown; can be homogeneous (fig. 34), in strong spiral bands (figs 32, 35), pale spiral bands (fig. 33) or axial bands (figs 38, 39). The outline varies from broad (fig. 32) to slender (fig. 38); from almost straight (fig. 35) to convex (figs 32-34); or deformed (figs 36, 37). The spiral ribs vary from outstanding (figs 33, 34) to weak (figs 38, 39). Among several other parameters. Morę details in Bequaert (1942: 8, pl. 1 figs 2-3; pl. 5, figs 1-6).

Head-foot (figs 377, 385). Pigmented by dark brown spots sparse in head and dorsal region of foot, other regions greenish beige. Head protruding. Snout dorso-ventrally flattened, broad, somewhat bilobed anterior margin. Tentacles long, stubby. Eyes dark, on smali ommatophores in middle-outer region of tentacles. Foot of medium size, without divisions; a furrow of pedał glands in anterior margin. Left insertion of mantle morę pos-terior than right one. Columellar muscle of about 1.5 whorls.

Operculum (fig. 69). Circular, brown, multispiral, nucleus central, fimbriated edge. Muscle scar elliptic near inner margin. Occupies entire aperture.

Mantle organs (figs 380,381,386). Mantle border entirely flanged by smali, somewhat uniform papillae; not pigmented or sometimes with brown filiform spots, perpendicular disposed. Mantle cavity of about 1.5 whorls. Osphradium long, ridge-like, with little morę than half of gili length; its anterior end about in same level than that of gili. Gili very long, discretely shorter than cavity and somewhat broad; filaments tri an gul ar, tip sharp, almost central; ctenidial vein broader than osphradium in its posterior half. Between gili and rectum a proportionally narrow space. Hypobranchial gland thin, inconspicuous. Adrectal sinus not visible. Rectum very broad, bearing elliptical, long fecal pellets compacted obliąuely.

Anus siphoned posterior from mantle border. Pallial gonoducts run at right margin, described below.

Circulatoty and excretory Systems (figs 380, 386). Heart similar to those of preceding species, aortas attached to gastric style sac and adjacent intestine loops. Kidney short, about 1/4 whorl, solid, white, with single lobe. Nephrostome slit-łike, in middle region of wali between kidney and pallial cavity.

Digestive system (figs 378, 379, 382, 385-389). Mouth in anterior extremity of snout, longitu-dinal, ventral, thick muscular. Buccal mass of medium size, almost ail within snout. Jaws two very smali triangular plates; pale beige; attached to a flaccid, transparent membranę inserted in dorsal wali, posterior to mouth. Pair of dorsal inner folds very broad (fig. 382), a smali median angle of each in they middle region, which marks aperture of : salivary gland ducts; folds gradually narrow in direction to esophagus; posterior regions of these folds with daik brown spots. Odontophore (figs 387- . 389) similar to those of preceding species. Distinctive features are: 1) radula very long, coiled ; in its posterior region; 2) m2 narrow; 3) mil with a i branch inserted in anterior extremities of j odontophore cartilages, without connection with ^;peribuccal muscles; 4) m7 part originating in adjacent region of subradular membranę (beyond from ml 1); 5) m8 very long and narrow. Radular i teeth (fig. 108): rachidian tooth with 5 cusp, central cusp several times larger than lateral cusps, a pair of i basal cusp; lateral tooth with 4 cusps being second j very larger and triangular; inner marginal tooth \ spoon-like, with 4-5 cusps, being lateral cusp larger; i outer marginal tooth similar to inner one but with 6- i 7 smaJler cusps. Salivary glands large, long, poste- ■ rior to nerve ring; right salivary gland with glandu-lar tissue also anterior to nerve ring. Esophagus with i two very long, narrow and shallow pouches, each | one with several oblique glandular folds; folds of i dorsal wali of buccal mass stay in base of each pouch, in transition, dark pigment present (fig. 382: ds). Stomach(figs 378,379) large, morę than half whorl. i Central pad very large and long, occupying almost entire ventral surface of stornach. Anterior chamber i short. Duet to digestive gland in anterior region of left border of central pad. Gastric shield broad. Crescentic ridge absent. Intestine and style sac fused • in a long distance (entire left region). Style sac with about half of remainder stornach length. Intestine,