140 REV. A. H. COOKE ON THE [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^, Reeve (figs. 5, 5 a). 



No special features. Formula 2.5-7-1-7-25. 



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. 



"O^ 



Several interesting facts follow on this investigation. In the first 

 place, the teeth of the radulse 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 Siisswasser-MoUusken Nord-Ost-Afrika's". 

 The resemblance amounts to identity ; in Isidora the central tooth 

 is squarish, bicuspid, the laterals tricuspid, the marginals serrate, 

 just as in these Australian ' PhyscB,' and the shells present no diff'er- 

 ence whatever. Fischer, therefore, is quite right' in regarding the 

 Australian and African genera as the same, and thus a most remark- 

 able link is established between the moUuscan 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 Conti- 

 nents, 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 Limncea. A comparison of the central tooth and 

 first lateral of Plan, corneus and of Limn, stagnalis (see figs. 9, 10, 



^ No-va Acta Ac. Nat. Our. xxxvii. 1875, Taf. iii. figs. '2-A. 

 2 Manuel de Conchyl. p. 609. 



