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Show 138 REV. A. H. COOKE ON T H E [Mar. 19, Professor Hutton, examining " Bulimus gibbosa, Gld. (Physa) ?," notices that the edge of the mantle is simple and not reflected over the shell; that the radula has 126 rows, with formula 27-1-27: he goes on to characterize the teeth at length. Bulimus variabilis, Gray (Physa), is also described as being similar in form of radula, rows 112, formula 18-1-18; and the belief is expressed that probably the other species of Physa described from New Zealand will all be found to belong to the same genus1. Professor Tate has expressed a belief that the sinistral spiral Pond-Snails of Australia have been incorrectly placed in the genus Physa. He remarks2 that in no instance has he found in the species those distinctions which characterize Physa as separate from Bulinus. He observes that the mantle-margin is neither expanded nor digitate, and he catalogues 10 species as Bulinus. Tapparone-Canefri describes3, as belonging to Physa, the new section Physastra with the single species Ph. vestita. From his description of the shell, however (form of Limneea, but sinistral, thicker than the common type of Physa ; surface not shining, but covered with a somewhat thick epidermis, which easily comes off when dry), it is plain that he is dealing with a specimen of the group now under investigation. He figures the specimens, but his examination of the animal was unfortunately not successful. The following species of this group have been examined1, and the results appended have been arrived at:- General Characteristics. Radula long, rather broad, consisting of 140-220 rows ; central tooth not equal in size to first lateral, bicuspid ; cusps rather blunt; laterals and marginals together about 30-40 in number; laterals 7-12, tricuspid ; cusps not much differing in length ; passage to marginals gradual ; marginals serrate, often much curved at extreme edge, where they become very small and less serrate. PHYSA GIBBOSA, Gld. (figs. 1, 1 a). Radula with about 144 rows; cusps of central tooth very blunt ; laterals 7-8, horizontal. Formula 22-8-1-8-22. Hab. Australia. PHYSA PROTEUS, Sowb. (figs. 2, 2 a). Radula with about 83 rows (specimen probably imperfect), very similar to gibbosa. Formula 27-8-1-8-27. Hab. Australia. 1 Trans. N.Z. Inst. xiv. 1881, p. 155. Bulimus must surely be a misprint for Bulinus, and the formula of B. variabilis is a little suspicious 2 Trans. Roy. Soc. S. Austr. v. 1882, p. 51. 1 " Fauna Malacologica della Nuova Guinea," Ann. M u s Stor Nat Genova xix. 1883. 4 All the specimens have been prepared by and are in the collection of Mr. H. M . Gwatkin, M.A., of St. John's College, Cambridge. |