256 
CYCLADiE. 
size^ some being twice as large as the others ; the 
largest were about 1 J- line long. 
When the siphons are very much extended, the 
difference in the length between the two is not so 
great as above, as it is the basal part of the siphons 
which appears to be the most extensile, the apical 
parts keeping the same relative length to each other 
that they did in the less extended state. 
I am informed that some British conchologists 
consider C. pallida to be the (7. lacustris of Dra- 
parnaud; it is very unlike the specimens I have 
received from France and the rest of Europe under 
that name. 
In company with the (7. pallida described in the 
last Number of the Annals,’^ Mr. Bowse finds 
another species of the genus, which is very distinct 
from the well-known and generally distributed (7. 
cornea in being subtriangular, which gives it much 
the external appearance of a species of Pisidium. 
I cannot identify it with any of the species in the 
British Museum collection, nor can I find any 
description or figure representing it in any of the 
works on European freshwater Mollusca; I there- 
fore indicate it as new. 
It most resembles some specimens which we have 
received as Cyclas tumida of Pfeiffer ; but I do not 
find any species under that name in Dr. Pfeiffer’s 
work. The Paddington Canal specimens are more 
inequilateral, longer, and more triangular, having a 
very distinct hinder slope. 
M. Deshayes considers (7. tumida as only a variety 
of C. cornea. 
