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originating in inner middle region of subradular membranę inserting in m7 and in anteriorextremity of cartiiages. Mass of tissue in region between odontophore and esophagus very tali (fig. 164: to). Radula (fig. 86): similar to those of preceding species, with following number of cusps: rachidian tooth with 7 upper cusps being central laiger; late-ral tooth with 5 cusps being sccond larger; margi-nal teeth with 5 terminal cusps. Buccal ganglia large^ with minutę dark spots (fig. 165). Anterior extremity of anterior esophagus with a pair of vestigial pouchcs, with minutę oblique folds in la-terał regions of large folds; these folds continuation from those of dorsal buccal mass wali. Esophagus narrow, without glands; inner, narrow, longitudi-nal folds. Stornach large and very complex (figs 157-160); central pad very large, oceupying most gastric length, with two longitudinal furrows (being one of them posterior-left) and a narrow anterior region; gastric shield differentiable; crescentic ridge large, surrounding posterior half of central pad, but not inserting in it; esophageal opening in a deep furrow, from which two folds begins and run to intestine origin (gf) where unitę one with other; two or threc ducts to digestive gland close one another, opening in esophageal deep furrow, near central pad left maigin; dorsal sorting area well developed having one narrow fold and a furrow lying its posterior margin, and a short rounded fold at left; style sac long, with style (fig. 161); intestine originating from two tali folds situated in anterior-left region of anterior gastric chamber, one of them lies in intestine as a typhlosole (fig. 160). Digestive gland lies from antero-ventral region of stornach and also 1.5 whorls posterior to it. Intestine separated from style sac, with two loops close to it (fig. 159). Rectum broad, flattened, running in a broad ad-rectal sinus; intcmally smooth surfacc, without folds. Anus siphoned near mantle border.

Genital system (figs 153-155, 163). Only females found. Ovary very smali, immerscd in posterior region of digestive gland near columella, color whitc. Oviduct white, narrow, lies columella. Before pallial cavity a narrow pericardial duet. Pallial oviduct very complcx, with posterior half closed; posterior extremity a single tubę; afterwards two folds begin and gradually becoming larger in a posterior deep flattened chamber (fig. 153: b 1); a ventral channel begins ventral to left fold (fig. 153: b2), runs ventrally to anterior opencd half of oviduct, and finishes in left furrow; upper cited posterior deep chamber runs dorsally attached to ventral channel, larger and morę complex: in its middle region two smali folds (fig. 154) well spaced with each other in right side, and two longitudinal broad glandular folds in its left side; these four folds finish gradually in level of oviduct aperture (figs 153, 155: ap), ventral and at right of ventral channel; anterior third of oviduct with a central, U-shaped in section, channeled fold, covered by two laminae, one in each side. Oviduct finishes posterior to anus close aperture of brood pouch. Aperture of brood pouch smali (fig. 150), sphincter-like, without inner structures except smali radial folds. Brood pouch a large sac (figs 150, 163), bulging behind head and intemally compressing esophagus to left. Intemally some sparse septa, and about 30 young specimcns from one to five whorls, being younger morę abundant (about 20). No visible mucus around young in brood pouch, however a transparent membranę surrounds specimens from one to two whorls.

Measurements (in mm). 34.0 by 14.7 (figured specimen);35.3 by 15.1;36.2 by 14.7;36.2 by 16.0; 34.0 by 14.3.

Distribution. Upper Parana Basin, Sao Paulo

State.

Habitat. The specimens were found crawling on sand in shallow water (0.5 to 1 m), in river and lakes with some flow.

Materiał examined. Brazil; Sao Paulo; Avarć city, Jurumin Dam, near Paranapanema, MZSP 28309, 70 specimens (J. Colfat col, 16/i/ 96); Jurumim Dam, Ribeirao das Posses River, MZSP 28288, 6 specimens (A.A.O. Afonso & R. Henry col., 21/ix/1996).

Obscrvations: A. tenuilabris was included in synonymy list of A. glabrum Spix, 1827 (from Prov. St. Sebastiani = Rio de Janeiro) by Nuttall (1990: 259), which also included A. behni (Reeve, 1860) (from Pernambuco), based on shell similarities. The idcntification of the specimens studied herein is maintained as^4. tenuilabris until a deeper knowledge on specimens from the other two typc localities, this ąuestion is then considercd opened. The identification of the materia! used here is mainly based on ccmparison with lots studied by Ihering (1902,1909), of MZSP, which restricted the locality from “Brazil” to practically only Sao Paulo drainages. The two specimens figured by