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Vol. 36(2), 2001

Digestive system (figs 348-358). Mouth and buccal mass similar to those of B. varium. Two broaddorsal inner folds of buccal mass (fig. 349), each one with a middle longitudinal furrow in their posterior region; these folds continue in anterior esophagus by a short distance; they suddenly finish broad and flattened. Odontophore (figs 353-355) also similar to that of B. varium, but shorter, with odontophoral cartilages somewhat circular and m 11 not connected to cartilages. Radular teeth (figs 104, 105): rachidian tooth narrow and tali, with 9 cusps being central cusp larger, no basal projections or cusps; lateral tooth with 9 cusps being second larger and terminal; marginal teeth rook-like, inner mar-ginal tooth with 6 smali cusps in each sidc and a shaip terminal larger cusp; outer marginal tooth without distinguishable cusp. Salivary glands smali, posterior to nerve ring. Middle and posterior esophagus without inner glands or folds. Stornach (figs 356, 357) also similar to that of B. varium, with short style sac and crescentic ridge sub-cylindrical; but with dorsal sorting area having fewer folds, and proximal intestinal region dark colored (fig. 358: ds). Intestine with single loop in right side of style sac. Rectum somewhat narrow (described above). Digestive gland with morę than four whorls posterior to stornach (fig. 348).

Genital system. Gonad in both sexes occupying superior region of digestive gland (fig. 348). Małe (fig. 359): pallial spermoduct broad, white in color, thick glandular, opened at almost all its length. Female (figs 348, 351, 360, 361): pallial oviduct very broad, almost all opened; outer lamina simple, thick glandular; inner lamina also thick; bursa copulatrix of considerable size in middle region of outer lamina, immerse in its wali, with a narrow anterior aperture. No other structures. No ovopositor.

Measurements (in mm). 3.7 by 1.4; 4.5 by 1.6 (figured specimens).

Distribution. From North Carolina, USA, to Santa Catarina, Brazil.

Habitat, similar to that of B. vańum, but appears to occur deeper.

Materiał Examined. Brazil; Sao Paulo; Ubatuba, Andorinhas Beach, 40 specimens, MZSP 25111 (IOUSP, 22/i/l 963).

Remarks on B. varium and F. dubia. Finelła dubia differs anatomically from Bittium varium in having 1) foot smaller and simpler (without furrows); 2) osphradium not clearly pectinate; 3) gili smaller; 4) fecal pellets longitudinal (not obliquely compacted) in rectum; 5) dorsal sorting area in stornach less developed; 6) ovopositor absent. Although, both species have the following similarities if compared with other studied ccrithioideans: 1) smali size; 2) inner chitinous layer of shell; 3) relatively smali snout; 4) intestine with similar loops and rectum narrow; 5) crescentic ridge of stornach short and roundcd, 6) posterior-median furrow of foot sole; 7) style sac short; 8) anterior-dorsal region of stornach and proximal intestine dark pigmented; 9) satellite fold around osphradium. These characters, some of them clearly synapomorphies, indicate a close relationship between both species. B. varium appears to be better regardcd as Diastomatidae, rather than Cerithiidae. However, further studies, mainly on type species of each taxon, are necessary for a definitive systematic placements.

F. dubia differs anatomically from Diastoma melanoides (Reeve) (cf. Houbrick, 1981 c) in having less mantle border papillae, snout smaller, operculum with nucleus morę central, radular lateral tooth with morę and smaller cusps, radular marginal teeth rook-like and salivary glands short. On the other hand, the pallial oviduct and stornach are similar. Houbrick (1981 c) brings interesting discussion on systematic relationship of the diastomatids, refening a close placement to the Cerithiidae, Potamididae and Melanopsidae.

F. dubia differs considerably in anatomical characters from F. pupoides Adams, 1860 and from F purpuneoaplicata Preston, 1905 (Ponder, 1994). F. dubia lacks so developed pallial tentacles, so extensible snout and aecessory structures of posterior region of pallial oviduct. These data show that a new revaluation of the generic attributions must be taken into consideration. However, F. dubia is maintained in Finella until a revision study of these taxa.

On the other hand, B. varium and F. dubia have similarity with Diala sp (Ponder, 1991), in shell shape, operculum, radular features, presence of large osphradium satellite fold, and central pad and crescentic ridge similar sized (“gastric folds” in fig. 8). Ponder (1991) pointed out a close relationship of Diala with the litiopids, and suggested a possible family rank, Dialidae.