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Campanile symbolicum); 2- smali (Serpulorbis decussatus) (Cl- 66, Rl= 0, not additive).

12.    Pedał gland furrow: 0= anterior only; 1= edge

of en tire sole (Campanile symbolicum) (Cl-100, RI= 100).

13.    Tentacles: 0= absent; 1= a pair anterior

{Serpulorbis decussatus); 2= single posteri-or {Doryssa atra); 3= several (Alaba incer-ta) (CI= 75, RI= 0, not additive).

The normal cerithioidean lacks any special pedał structure, such as tentacles. This lack is shared with basal caenogastropods. Although the 3 species cited above have foot tentacles. The position of these taxa in the obtained tree suggested independent origin ofthose foot accessory structures.

14.    Posterior funow of pedał gland: 0= absent; 1 =

present(5im«m varium, Finella dubia, Alaba incerta) (CI= 50, RI= 66).

Operculum

15.    Nucleus situation: 0= central; 1= eccentric

(cerithids, Finella dubia, Alaba incerta)-, 2= subterminal (thiarids, Supplanaxis nucleus) (CI= 66, RI= 92, additive).

16.    Type of coiling: 0- multispiral; 1 = paucispiral

(cerithids, Finella dubia, Alaba incerta)-, 2-concentric (unguiculate) (thiarids, Supplanaxis nucleus); 3= absent {Serpulorbis decussatus) (CI= 75, RI= 87, not addictive).

17.    Outline: 0= circular; 1=sub-elliptical (cerithids,

Finella dubia, Alaba incerta); 2= elliptical (thiarids, Supplanaxis nucleus) (0=100, RI= 100, additive).

The multispiral operculum with central a nucleus, the standard in vetigastropods and found in some cerithioideans (Modulidae, Campanilidae, ■Rnritellidae, Vermetidae, Batillariidae, Pleuroceridae and Cerithideidae), is regarded as plesiomorphic. The concentric sculptures (unguiculate) operculum, with almost terminal nucleus, resembling those of most neogastropods, is also found in some cerithioideans (Planaxidae and Thiaridae). Observing the tree, it is possible to notę that this subterminal nucleate, unguiculate type is the last step of an evolutionary lineage, leaving from multispiral central-nucleate type, having the paucispiral, eccentric nucleate operculum as intermediary (present in Cerithidae, Diastomatidae and Litiopidae).

The sampled vermetid, S. decussatus, lacks operculum, as well as all members of the genus Serpulorbis (see Morton, 195la; Hughes, 1983). However, most vermetids possess multispiral, circular opercula (Morton, 195Ib, c; Hughes, 1983).

Cephalic tentacles

18.    Eye site: 0= basal; 1= sub-basal (all cerithioideans except the listed following); 2= middle (Af. modulus, Batillaria minima, Campanile symbolicum) (CI= 40, RI= 25, additive).

In archaeogastropods, the normal site of the eyes is the extemal base of the tentacles. This character is not found in the cerithioideans examined, all of which have the eyes located slightly over the tentacle base outer surface. In this way, the proximal region of the tentacle works as a smali stalk for the eyes. This is elear observing living, crawling animals. In some cerithioideans, such as Modulus, Batillaria and Campanile, the eyes are located in the middle level of tentacles length, character regarded as extreme link. The eyes not just in the tentacles base appears to be the rule among the caenogastropods, as this is found in littorinids and most of higher groups.

19.    Transverse section and site: 0= cylindrical and

dorsal; 1= flattened and dorsal {Campanile symbolicum); 2- cylindrical and ventral {Serpulorbis decussatus) (CI= 100, RI= 100, not additive).

20.    Ommatophore: 0= absent; 1= peduncle

{Supplanaxis nucleus, M. modulus, Cerithium atratum, Batillaria minima, Campanile symbolicum); 2- sessile (pleurocerids) (01= 28, RI= 58, additive).

The ommatophore is defined herein as a smali secondary stalk in the base of eyes, away from the tentacle axis but originated from it. The eyes to be located away from the tentacles. In the case of pleurocerids, the ommatophore has a very