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of some other caenogastropods [e.g., littorinids (Simone, 1998), tonnids (Simone, 1995b), nassarids (Simone, 1996b)]. In some in hydrobioids, both conditions can occur, showing that this character (single or double duet to digestive gland) can change. Two examined species {Campanile symbolicum and Serpulorbis decussatus) have 2 ducts to the digestive gland. In S. decussatus, these ducts are widely separated with each other and even the digestive gland is divided in two separated lobes. The condition of a double duet is regarded as plesiomorphic, but the analysis of the tree revealed the possibility of reversion. If so, these two species (and maybe the members of each family) developed from species with single duet. This has been observed in examined Aylacostoma spp.; A. exop\icata and A. ci have single duet, while A. tenuilabris has 2 and even, in some specimens, 3 ducts to digcstive gland (inserted directly in stornach). These data, in congener species, demonstrates that reversion to a double duet in the stornach is possible. Due to the proximity of A. tenuilabris digesti.ve gland ducts in stornach, this species State has been scored in same State of other Aylacostoma spp.

98. Style sac and intestine: 0= entirely fiised; 1 = separated by a constriction (pleurocerids, Turritella hookeri, cerithids, Finella dubia, Alaba incerta, Batillaria minima); 2= entirely separated with each other (thiarids, M. modulus, Cerithidea costata) (Cl= 22, RI= 41, additive).

The assumed plesiomorphic condition of the sepaiation of the style sac from the intestine is found in littorinids, with almost no separation between the intestine and style sac (present in Supplanaxis, Campanile and Serpulorbis. Separation of the intestine and style sac by a constriction, but united anatomically by a narrow aperture; is seen in pleurocerids, Cerithium, Bitiium, Finella, Alaba, Batillaria and Turritella. A third condition has the intestine altogether separated from the style sac sińce their origin; this condition having found in thiarids, Modulus and cerithideids. The intestine separated from style sac is regarded as the apomorphic end of a transformation series, and is homoplastie with hydrobioids. (An interesting additional discussion onalimentaiy canal of some cerithioideans is found

also in Graham, 1939.)

99.    Pre-intestinal fold: 0= absent; 1= double

(thiarids, Campanile symbolicum); 2= single (Doryssa atra, D. macapa, Pachychilus sp) (Cl= 50, R1= 66, not additive).

100.    Intestinal typhlosole: 0= absent; 1= present (thiarids, Campanile symbolicum) (Cl= 50, RI= 75).

101.    Fold at left, posterior to those folds which pre-

cede the intestine: 0= absent; 1= present {Aylacostoma spp) (Cl= 100, RI= 100).

The ventral inner surface of the stornach of some cerithioidean species is very complex, with folds and sorting areas. Most of the searched characters are autapomorphic, except those above listed. The nomenclature follows in generał that of Houbrick papers.

102.    Anterior chamber of stornach: 0= absent; 1 = present (all cerithioideans) (Cl= 100, RI= 100).

The anterior chamber, delimited posteriorly by a constriction, generally shows a smooth surface and precedes the intestine-style sac apertures. Presence of this anterior chamber, absent in all examined outgroups, is regarded as apomorphic.

103.    Style sac length: 0= about 1/2 stornach length

(or 1/4 whorl); 1= very long (about than 1 whorl) {Cerithidea costata); 2= inconspicuous {Campanile symbolicum, Serpulorbis decussatus) (CI= 40, RI= 0, not additive). The style sac of Campanile and Serpulorbis is hard to delineate. In the former species it maybe reduced or only a smali part of the intestine, and in Serpulorbis it may be very widely open to the stornach (see also Morton, 1951 a, fig. 9). In contrast Cerithidea has a very long of style sac, its length morę than half a whorl, and it invades the pallial cavity (see also Driscoll, 1972).

104.    Esophagus aperture: 0= anterior; 1= middle (all cerithioideans except Alaba incerta, Batillaria minima and S. decussatus); 2= posterior {Serpulorbis decussatus) (CI= 40, RI= 57, not additive).

The cntrance of esophagus in the stornach