| OCR Text |
Show 140 REV. A. H. COOKE ON T H E [Mar. 19, PHYSA SINUATA, Gld. (figs. 3, 3 a). Radula with about 83 rows (specimen probably imperfect); laterals rather more extensive than in the other species ; outer cusp very small. Formula 25-12-1-12-25. Hab. Viti Islands. PHYSA TABULATA, Gray (figs. 4, 4 a). Radula with at least 220 rows; extreme marginals very much curved. Formula 32-8-1-8-32. Hab. New Zealand. PHYSA ALICI^E, Reeve (figs. 5, 5 a). N o special features. Formula 25-7-1-7-25. Hab. Australia. PHYSA MULTISTRIGATA, Tate (figs. 6, 6 a). Formula 30-8-1-8-30. Hab. Australia. PHYSA PHYSOPSIS, Cooke (figs. 7, 7 a). Radula large, rows about 140 ; laterals numerous. Formula 30-9-1-9-30. Hab. Australia. PHYSA SCALARIS, Dkr. (figs. 8, 8 a). Rows about 140, not so much curved as in the other species; passage between laterals and marginals not distinctly marked. Formula about 25-7-1-7-25. Hab. Angola. Several interesting facts follow on this investigation. In the first place, the teeth of the radulee bear a very striking resemblance to those of the African genus Isidora, Ehrenb. So far as I am aware, the radula of Isidora has only once been figured, namely by Jickeli in his 'Fauna der Land-und Susswasser-Mollusken Nord-Ost-Afrika's'1. The resemblance amounts to identity; in Isidora the central tooth is squarish, bicuspid, the laterals tricuspid, the marginals serrate, just as in these Australian ' Physce,' and the shells present no difference whatever. Fischer, therefore, is quite right'2 in regarding the Australian and African genera as the same, and thus a most remarkable link is established between the molluscan fauna of Australia and Africa, a link in the chain of evidence already afforded by the existence of the carnivorous Land-Shells (Rhytida) in both Continents, and, amongst the marine Mollusca, by .the occurrence of identical species of such littoral shells as Purpura and possibly of Littorina. In the next place, the relation of the group is much closer to Planorbis than to Limneea. A comparison of the central tooth and first lateral of Plan, corneus and of Limn, stagnalis (see figs. 9, 10, 1 Nova Acta Ac. Nat. Cur. xxxvii. 1875, Taf. iii. figs. 2-4. 2 Manuel de Conchyl. p. 509. |
