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. 
Whaorl 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, 7b. 
THE END. 
COX AND WYMAN, PRINTERS, GREAT QUEEN STREET, w.c. . 
