MB. E. A. SMITH ON FEESHWATEE SHELLS OF AUSTEALIA. 255 



On the Freshwater Shells of Australia. By Edgae A. Smith. 

 (Communicated by Dr. J. Mueie, F.L.S.) 



[Eead April 21, 1881.] 



(Plates V.-VII.) 



Ofe knowledge with respect to the freshwater shells of the 

 Australian continent is comparatively in its infancy. Although 

 more than one hundred and fifty species are now known (many 

 of these but unsatisfactorily), this, in comparison with the extent 

 of the country, is but a small number, probably not a moiety of 

 those existing; and there is but little doubt that, in the course 

 of time, when the known rivers and lakes and those as yet un- 

 explored have been thoroughly investigated, many new species 

 will be discovered. 



Judging from those with which we are now acquainted, no very 

 strange forms are to be expected ; for, with the exception of the 

 elongate U/iio novce hollandice, with its tuberculose surface and 

 black epidermis, there are scarcely any except very ordinary 

 types among them. The existence of a species apparently be- 

 longing to the African genus Fhysopsis is certainly remarkable ; 

 and another shell, described as a Mycetopus, if truly belonging 

 to that genus, is interesting as the representative of a South- 

 American group. However, it is not at all improbable that, 

 whenever the animals inhabiting these two shells are examined, 

 they will prove very different from those belonging to the genera 

 to which they have been referred. 



A few of the species hereafter enumerated are not peculiar to 

 Australia ; and among them may be instanced the ubiquitous 

 Melania tuberculata, M. amarula, Neritina crepidularia, and 

 N. puUigera. The most numerously-represented genus is Physa. 

 Of this group no less than 52 distinct forms have been de- 

 scribed. Some of these may eventually prove to be mere 

 varieties, jDOSsessing no essential constant specific characters; 

 but others new to science will in all probability ere long be 

 added to the list. Tlnio is the next most important group in 

 point of numbers, being represented by 17 different species. 

 Then follows Melania with 12, Neritina Yiith. 10, Limncea v{it\i 11, 

 Paludina and CorUcula each having 9 species, Hydrohia ? 6, 

 Planorbis 6, SpTicerium and Bithyniu4i, Pisidium 3, Segmentina 2 ; 

 and, finally, Tatea, Amnicola ?, Paludinella ?, Larina, Oahhia, 



linn. JOUKN, — ZOOLOGT, VOL. XYI. 18 



