Fig. 43- 
Planorbis isingi, side 
view. 
Segmentina victoriae, are found in slow-running streams and 
stagnant water. Two snails, both “right-hand” twisted, are 
occasionally found; they are the Paper Shell, Myxas papyracea, 
about three-quarters of an inch in length, and the more slender 
subaquatic Pond-snail, Limnaea subaquatilis, measuring about 
half an inch long. 
Another “left-handed” snail is the Red Pond-snail, Isodorella 
rubida, readily distinguished by its dark, reddish-brown colour 
and swollen shape. Three freshwater bivalves are found: 
Angas’ Freshwater Cockle, Corbicula angasi, Macgillivray’s Orb 
Shell, Sphaerium macgillivrayi, and Etheridge’s Pea Shell, 
Pisidium etheridgi. The first may measure one inch in length 
whereas the others rarely measure a quarter of an inch. It is 
Fig. 44 - 
Plan orbis isingi, top 
Fig. 45 - 
Segmentina victoriae 
Fig. 46. Ftg. 47. 
Corbicula angasi. Pisidium etheridgi. 
Fig. 48. 
Sphaerium 
macgillivrayi. 
quite probable that many more kinds of mollusca, both native 
and introduced, may be discovered when a thorough, systematic 
search is made. 
/ ~*ag e E ig hty-five 
