244 
INDEX. 
W. 
Water snails, characters of, 181; habits and reproduction 
of, 182 ; peculiar sensation produced by, 183 ; synop¬ 
tical list of genera of, 184 ; decollation of the spire of 
the shells of, 185 ; dispersion of, 188 ; disappearance 
and reappearance of, 192. 
Water-breathing snails, 44. 
Whorl , 44. 
Whorl snails, 158. 
Z. 
Zebra mussel, description of, 20 ; foot, byssus , and apertures 
of, 21 ; discovery of, ib .; introduction of into Britain, 
22 ; action of light on, 23 ; habits of, 24. 
Zua lubrica, 151; distinction of from Zua lubricoidea, ib. 
THE END. 
COX AND WYMAN, PRINTERS, GREAT QUEEN STREET, W.C. 
