THE HAMILTON ASSOCIATION. 89 



prove to be different to the above, while Limna'a catascopium 

 will, I expect, be found in Lake Ontario. 

 Physa gyrina, Say. 



Scarce in different pieces of water in this neighborhood. 

 Physa ancillaria. 



A few specimens were picked up on the shore at Port Dover, 



and it may be found here in the Lake. 

 The Rev. G. W. Taylor has retained nearly all my Physas for 

 further examination. I expect to get at least two more 

 species from among them. 

 Bulinus hypnorum, Linn. 



Abundant in small streams running through open woods. 

 Some fine specimens have been secured this year. 

 Planorbella campanulata, Say. 

 Helisoma trivolvis, Say. 

 Helisoma bicarinatus, Say. 



The last three species abound in stagnant pieces of water in 

 our district. 

 Segmentina armigera, Say. 



A single specimen was taken in Dundas Marsh on May 6th. 

 A peculiarity of this shell is that it has five small teeth at 

 some distance from its mouth ; in fact to see these teeth 

 plainly it is necessary to break away a portion of the shell. 



Gyraulus . 



Several species from Hamilton Bay and Dundas Marsh have not 

 yet been determined. G. deflectus and G. hirsutus should 

 be among them. 

 Ancylus rivularis, Say. 



A few specimens were found attached to the valves of dead 

 Unios, cut out of the ice after the storm of Jan. 9th. 



TERRESTRIAL GASTEROPODA. 



(OPERCULATE.) 

 POMATIOPSIS LAPIDARIA, Say. 



A terrestrial species of a fresh-water genus. This shell is new 



