Baker — The Mollusccm Fauna of Western New York. 89 



stumpy shell with the aperture longer than the spire. An- 

 other form occurs which has a longer spire, as long as the 

 aperture, and runs into L. expansa Hald., which latter does 

 not seem to me to = L. palustris MUller, but is rather a vari- 

 ety of catascopium. A peculiar monstrosity was found by 

 Master Hall at station 4, in which there was a large longitu- 

 dinal ridge behind the peristome, the latter being much 

 expanded, flaring, and the aperture twisted out of shape. 

 Catascopium is found on stones and sticks in water from a 

 few inches to several feet in depth. 



107. LiMNAEA DESiDiosA Say. 

 Stations 3, 5, 6, 9, 11 and 15. Monroe County (Walton). 

 Found commonly on sticks and stones, and occasionally in 

 Spirogyra. Considerable variation is found among the speci- 

 mens collected, some being long and narrow, while others are 

 short and stumpy. The aperture is sometimes a little longer 

 than the spire. 



*108. LiMNAEA CAPERATA Say. Pittsford (Walton). 



*109. LiMNAEA PALLIDA Adams. Erie Canal (Walton). 



110. LiMNAEA HUMiLis Say. 

 Station 11. Common and typical. 



Subfamily Planorbinae. 



Genus Planorbis Guettard. 

 Section Planorbella Hald. 



111. Planorbis campanulatus Say. 



Stations 5, 6 and 9. Pittsford (Walton). Very common. 



Section Helisoma Swainson. 



112. Planorbis trivolvis Say. 



Stations 3, 4, 5, 6, 8, 10, 15 and 17. Charlotte (Walton). 

 Common everywhere and extremely variable. Very frequently 

 distorted. 



