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Show 1889.] SO-CALLED PHYS.E OF AUSTRALIA. 137 relationship between these groups of the South Pacific, which is already indicated by the distribution of Rhytida, Janella, and Placostylus. The object of this paper is to show that these so-called ' Physce,'' the sole claim of which to the title is that they are sinistral freshwater- shells, are not Physce at all, but a group of sinistral Limnaeidse, characteristic of the geographical area above indicated, and also of another part of the world, where their presence is of extreme interest. This view rests primarily upon an examination of the radula of some of the species concerned. As is well known, the radulse of the Physidse and the Limnseidae are essentially different, and tend to remove Physa much further away from Limneea than are either Planorbis or Ancylus. Fischer describes them as follows1:- PHYSID^E. LIMNTEIDJE. Radula composed of teeth ob- Teeth of the radula in hori-liquely arranged ; central tooth zontal rows, bi- or tricuspid [cen-multicuspid; laterals and mar- tral tooth bi- or tricuspid, never ginals pectinate or serriform, and multicuspid] ; marginal teeth provided with a special narrow serriform ~. appendage on the upper and exterior edge. In the ' Journal of Conchology,' v. 1887, pp. 241-243,1 described, under the name of Limneea physopsis, a new species of these Australian ' Physce.' The reasons given for believing the species to be Limnseidan and not Physidan were based on (1) a consideration of the radula, and (2) the general facies of the shell. It was suggested, purely on grounds of general similarity of shell, that two other Australian species of ' Physa,' viz. P. hainesii, Tryon ( = latilabiata, Sowb.), and P. newcombi, Ad. and Ang., were also Limnseidee. Since that date several other species of this group of 'Physa' have been examined, and with similar results. It may at once be asserted that, in spite of the 52 or 54 species enumerated, Physa has yet to establish its claim to be an inhabitant of Australia. Every species as yet, which has been examined anatomically, turns out not to belong to that genus; and I am strongly of opinion that further investigation of the animals of the species as yet known only by the shells will afford more evidence of a similar kind. The note of suspicion has already been sounded more than once with regard to these Australian Physce. Mr. R. M . Johnston has noticed a " peculiar arrangement" of the lingual teeth in P. tasmanica, the medials of which are 2-cuspid, the laterals 4-, £-, and 6- cuspid, the extreme ones having a resemblance to the closed digits of the hand 3. 1 Manuel de Conchyliologie, pp. 503, 510. 2 It may be remarked that this description is inadequate, so far as Ancylus proper is concerned. 3 Proc. Roy. Soc. Tasmania, 1878, pp. 19-29: he uses the term laterals to include marginals as well. |