. Bulletin of the British Museum (Natural History). PEBASIAN MOIXUSCAN FAUNAS 231. Fig. 203 Recent distribution of Hemisininae: map based on very few authenticated records. 9, Hemisinus; -k, Aylacostoma; A Basistoma; ft Longiverena; O, Verena. Inset: H. brasiliensis (S. Moricand), x 1; A. glabrum Spix, x 1; B. edwardsi Lea, x ; L. tuberculoid (Spix), x ; V. crenocarina (S. Moricand), x ; all Brazil. Aylacostoma preserved or whether no embryonic shells were ever present in these particular individuals. Specimens examined have included representatives of the type species of
. Bulletin of the British Museum (Natural History). PEBASIAN MOIXUSCAN FAUNAS 231. Fig. 203 Recent distribution of Hemisininae: map based on very few authenticated records. 9, Hemisinus; -k, Aylacostoma; A Basistoma; ft Longiverena; O, Verena. Inset: H. brasiliensis (S. Moricand), x 1; A. glabrum Spix, x 1; B. edwardsi Lea, x ; L. tuberculoid (Spix), x ; V. crenocarina (S. Moricand), x ; all Brazil. Aylacostoma preserved or whether no embryonic shells were ever present in these particular individuals. Specimens examined have included representatives of the type species of four genera, Hemisinus lineolatus (Wood), Verena crenocarina (Moricand), Longiverena tuberculata (Spix) and Basistoma edwardsi Lea. Embryonic shells of one other living species, Hemisinus globosus Reeve, here placed in the synonymy of H. kochi (Bernardi), and two young juveniles of fossil Verena browni (Etheridge) obtained from washings from the Puerto Narino deposit have also been studied. All the embryonic shells so far examined have features in common. The shell has a hemispherical, cup-like, origin and is, for the first whorl or so, virtually planorbiform. After this, the whorl translation rate increases rapidly so that the embryonic shell takes on a form increasingly reminiscent of shells mature enough to have enjoyed a free existence. In all the examples studied, the sculpture typical of the early teleoconch soon appears. This varies considerably in the taxa examined. For example, the later embryonic whorls of H. lineolatus are virtually smooth, whilst those of Basistoma edwardsi arc strongly carinatc. Genus BASISTOMA Lea, 1852 Type species. Basistoma edwardsi Lea, 1852: 296; pi. 30, fig. 1, by original designation. Recent, Rio Tocatins, eastern Brazil. No other assigned species. Diagnosis. Turritelliform Hemisininae with numerous whorls; spiral sculpture of numerous ribs on early whorls, reducing in strength on later whorls, eventually dying away altogether; no collabra
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