THE HAMILTON ASSOCIATION. II7 



Planorbis parvuSj Say. 



Common along shores of Bay and Marsh, and in some streams. 



Planorbis nautileus. 



Occurs in a small piece of marsh at the junction of Hamilton 

 Bay and the Desjardines Canal. A very tiny shell, the smallest 

 water shell known to me ; is hairy. The Rev. G. W. Tay- 

 lor in naming it states that it is identical with the English 

 P. nautileus ; from its small size is difficult to find ; if an 

 introduced shell it would be interesting to know by what 

 agency it reached its present habitat ; do not know that it has 

 been taken anywhere else in North America. 



SUB-GENUS PLANORBULA, HAIDE. 



Segmentina armigera. Say. 



Has been taken in some abundance in the marsh toward Dun- 

 das, attached to dead leaves lying in the water. 



SUB-FAMILY ANCYLIN^. 

 GENUS ANCYLUS, GEOFFROY. 



Ancylus rivularis, Say. 



Occurs in the Dundas Marsh and Hamilton Bay, a small colony 

 found attached to sunken sticks in a small stagnant piece of 

 water. 



ORDER PECTINIBRANCHIATA. 

 FAMILY VALVATID^. 

 GENUS VALVATA, MULL. 



Valvata tricarinata, Say. 

 Hamilton Bay, common. 



Vavata sincera, Say. 



Hamilton Bay and Dundas Marsh, not so common as the last. 



FAMILY VIVIPARID^. 

 GENUS melantho, Boivditck. 

 Melantho decisus, Say. 



Hamilton Bay. Some very fine specimens taken from the An- 

 caster Creek, near its junction with the marsh. A few re- 

 versed specimens have been taken. 



