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Arquivos de Zoologia

439) pair large, situated in base of thiek muscles. Dorsal region of buccał mass simple, without inner folds. Odontophore (figs 435-438) with following distinctive features: 1) a rotation of odontophore, being some intemal structures up side down in relation to those of preceding species; 2) insertion of jaws and peribuccal muscles somewhat horizon-tal and in posterior region of m4; 3) m5 short, inserting in middle region of radular ribbon, situated in posterior extremity of odontophore; 4) m4 dorsal and posterior, part situated down of subradular cartilage; another annex muscular bridge present beyond that normal connection with tissue on radula, dorsal to it and fused with outer tissue of buccal mass; 5) m2 absent; 6) mlO very thick and broad, inserted close to m5; 7) mil running posteriorly, without connection with cartilages nor with peribuccal wali; 8) m7 originating part from mil and part from adjacent region of subradular membranę; 9) m8 very broad but short. Radular teeth (figs 112, 113): rachidian tooth with 7 cusps being central cups veiy larger, a pair of basal, late-ral projections; lateral tooth with 3 cusps being first cusp laiger and terminal; marginal teeth rook-like, without cusps, apex sharp; inner marginal tooth broader than outer one. Pair of buccal ganglion close to with each other, near median linę (fig. 439). Esophagus broad, thin walled, without inner folds or glands, begins in dorsal and not in posterior side of buccal mass. Stornach (fig. 432) very lai^e and long, about 1/5 of total soft parts length. Esophageal insertion in left side and very posterior, from it a broad furrow begins and contours posterior gastric extremity, edged by two narrow folds. Two ducts to digestive glands; that anterior ample, situated in middle-ventral region of stornach, edged anteriorly by a Y-shaped fold; that posterior also ample, situated in posterior gastric wali, attached to posterior digestive gland. A dorsal fold, longitudinal, median, with posterior extremity in level of anterior duet to digestive gland, gradually narrows into near intestine origin, Other smali and short fold ventral to posterior duet to digestive gland. Style sac unclear, but probably situated in right side of dorsal fold (fig. 428). Intestine origin in anterior cxtremity of stornach. Intestine somewhat broad and of uniform weight; after stornach towards right and posteriorly, immerse in anterior digestive gland; runs obi iquely some distance and afterwards towards anteriorly; near posterior limit of pallial cavity bears a loop and newly towards posterior lying right region of visceral mass; finally towards anterior abruptly, runs ventrally to kidney and emer-ges in pallial cavity. Rectum and anus described above. Digestive gland distinct in being two separated lobes (figs 430, 432); that anterior very short, at left and posterior to kidney (dd 1); that posterior very longer, with length about 1/3 of that of soft parts (dd2); between both glands no connection, only gastric wali visible. Both digestive glands with apparently similar tissue.

Gcnital system (figs433,434). Only female examined. Oviduct restrict to a side of visceral mass, from posterior extremity to stornach, on posterior digestive gland. Oviduct cross ventrally stornach and anterior digestive gland; in left-pos-terior region of pallial cavity inserts in left extremity of pallial oviduct; before its aperture, inserts a smali, sac-like seminal receptacle, immerse in outer lamina. Albumen and capsule glands smali, situated at left and anterior to oviduct aperture. After some distance, pallial oviduct suddenly expands, after gradually narrows. Pallial oviduct closed at about 1/10 of its posterior length, rcmainder an opened groove with thick-glandular walls; finishes posterior to anus.

Measurements (in mm). 41.0 by 9.7 (figured specimen).

Distribution. From North Carolina, USA, to Rio de Janeiro, Brazil.

Habitat. Sessile, attached to corals and rocks, sometimes on gorgonians. Infratidal lcvcl.

Materiał examined. Brazil; Espirito Santo; Guarapari, 2 specimens MZSP 28347 (Coltro leg.).

Remarks. S. decussatus differs anatomically from S. zelandicus (Quoy & Gaimard, 1834) (cf. Morton, 195 la) in having poor pigmented head-foot, gili filaments narrower, and apparently other organization of pedał mucous gland and oviduct. The anatomical data of S. decussatus, however, indicates a double modę of feeding: eiliary feeding by food grove, and by mucus string with the presence of pedał tentacles and great development of pedał gland. This double modę of feeding is found in S. zelandicus (cf. Morton, 195 la) and Yermetus novaehollandiae (Yonge, 1932). Several organs of S. decussatus, in addition, appear to work up side down in relation to those of other cerithioideans. This is morę evident by position of cephalic tentacles (ventral in head) and by