THE FRESHWATER MOLLUSCA OF VICTORIA 
101 
throughout the State, but so much misunderstood that I have 
thought it advisable to reproduce the original description on 
a later page, together with that of B. nigra Q. and G. 
In the Transactions of the Royal Society of South Austra- 
lia, 1882, p, 76, Professor Tate, in a List of Victorian Fresh- 
water Pulmoniferous Snails, includes Limnaea viridula Tate, 
from Murndal, Hamilton, and Dr. Cherry, Proc. Roy. Soc. 
Viet., 1896, p. 183, identifies a form from the headwaters of 
the Winmiera as Limnaea venustula. After careful search I 
have failed to locate descriptions of these species and suggest 
that they are manuscript names only. 
Perhaps the most perplexing Victorian freshwater molluscs 
are the species now referred to the genera Ameria and Tsi- 
dorella, but formerly placed under Phgsa, BuUinus, Isidora, 
and Amplexa by various authors. Of recent years these 
freshwater snails have attracted attention as intermediate 
hosts for sheep fluke and possible hosts of Bilharzia. Hedley, 
in his Notes on the Victorian Species of BuUinus (Rec. Aust. 
Allis., 1917, p. 1) writes: “This group presents the student 
with exceptional difficulties. The species appear to vary 
extremely and to limits not yet ascertained. AVith the 
honourable exception of Tate’s Essay in the Zoology of the 
Horn Expedition, the literature has multiplied names and 
ignored A^ariation. A chance handful from any pool is likely 
to present individuals with a longer and a shorter spire. The 
first lesson to be learnt in studying this group is how change- 
able a character is this elevation of the spire. The presence 
or absence, spacing or punctuation, of spiral sculpture, can 
not be used as a safe guide to specific differentiation. These 
features are the imprint of spiral threads or lines of cilia in 
the epidermis. But the epidermal coat varies in development 
according to local conditions, so that lines of cilia, which 
would apparently be otherwise developed, seem to be repressed 
in unfavourable environment. Yet some geographical series 
suggest that there are species which never develop such ciliae. 
A more abundant supply of lime allows a deposit on the inner 
lip and hence longitudinal streaks that mark previous rest 
stages.” 
Although Hedley adds that no positive conclusions are 
adA^anced, his article considerably clarifies the nomenclature 
of these puzzling forms. 
In regard to distribution, haphazard dispersal is effected 
in many ways ; some molluscs are transported by water-plants, 
others by animals, and by these means newly formed ponds 
and creeks are populated. B. C. Cotton gives an interesting 
