Ancylus parallelus. Hald. Dark, narrow, more common. 



On plants. 



The remaining fresh water snails close the aperture with 

 a horny door, or operculum, attached to the snail. 

 Valvata tricarinata. Say. Small, whitish, whorls with 

 sharp keels, common. Ecarinate varieties in On- 

 ondaga lake. 



sine-era, Say. Brown, with ribs, no keels, habits 

 different from the last. Marshy spots on Seneca 

 river, rare. 



The Melanthos are green or greenish, large, solid, varia- 

 ble, viviparous, found in all waters but Onondaga and 

 Cross lakes. Muddy bottoms Approaching other species. 

 Melantho decisus. Say. Green, worn at apex, common, 

 integer. /Stoy. Similar, longer and more perfect, 

 rarer. 



rufus. Hald. Shorter, grayer, polished, rosy with- 

 in. Found only in canals and at Baldwinsville. 

 Abounds in canal. 



Lioplax subcarinatus. Say. Smallei> more expanded, and 

 the six whorls more rounded than the last. But one 

 found, not typical. Canal; found also in the Hudson. 

 Bythinia tentaculata. L. An introduced European shell 

 found by me at Oswego in 1879, now abundant at 

 Syracuse. Resembles Melantho, but is small, yel- 

 lowish, grey or red. 



Bythinella obtusa. M. Tand. Resembles Papa, Erie ca- 

 nal, rare. 

 Gilia nltilis.Lea. -Small, green, orbicular. Abundant 



in canals. 

 Somatogyrus isogonus. *Say. Similar, rare. 



The genus Amnicola contains minute shells like the Me- 

 lantho, but perforate. Abundant in all waters on plants. 

 Amnicola Sayana. Antli. Elevated, six whorls, rare. 

 Erie canal. 



Cincinnatiensis. AntTi. Rather slender, five whorls. 

 Canal. 



orbiculata. Lea. Depressed, orbicular, 

 porata. $ay. Perforated, round, common, 

 pallida. Hald. Paler and slender, rarer. Ponds, 

 limosa. Say. Small, bulbous, common, 

 lustrica. Say. Small, very slender, rarer, 

 grana. Say Very small. Seneca river. 



