THE NAUTILUS. 91 



Lynwsea, stngnalis Linn. Canadarago Lake. 



Lymiifp.a cohundlo. Say. Allan, Weaver Lakes. 



Lynmcea palustris Miiller var. Canadarago Lake, Otsego Lake. 



Fliysa ancillaria Say. Allan Lake. 



Pliysa Iteteroslroplia Say. Canadarago and Otsego Lakes and 

 many si reams. 



Planorbis fn'roh-i's Say. Allan Lake. 



rianorbis dilatoius Say. Canadaraga Lake. 



Planorbis rampanulatus Say. Canadarago Lake. 



rinnorbis bicarinatus Say. Sunset Creek, Canadarago Lake. 



Planorbis exacutus Say. Near Weaver Lake. 



Plnnorbis deflectus .Say. Young's Lake. 



Planorbis ulbns Miiller. Allan Lake, Otsego Lake. 



Ancylus rioihiris Say. Oak Creek. 



Anzylus tnrdus Say. Weaver Lake. 



AUCI//US fuscus Adams. Allan Lake. 



Ancy fits paralle.lus Hald. Town Creek. 



Sphcerium simile Say. Sunset Creek, Town Creek, Allan Lake, 

 Weaver Lake. 



Sphcerium rhomboideum Say. Allan Lake. 



Spluerium striatinum Lam. Sunset Creek. 



Plsidiutn ventricosum Prime. Canadarago Lake. 



Pisidiitm novcboracensc. Prime. Canadarago Lake. 



Lampsilis radiatus Gmelin. Canadarago Lake. 



Slrophitus edentulus Say. Sunset Creek. 



Ano'Ionta marghmta Say. Weaver Lake. 



Alasmidonta undulata Say. Sunset Creek. 



Unio complmtitus Solander. Oak Creek. 



A NOTE UPON THE INSUFFICIENCY OF THE OFEKCULUM AS A BASIS 

 OF CLASSIFICATION IN BOUND-MOUTHED SHELLS. 



I5Y L. P. GRATACAP. 



In 1801 Lamarck established the genus Cyclostoma which he 

 made for the reception of a very miscellaneous and unclassified group 

 of shells, characterized however by certain common features as 

 the entire round aperture, continuous peristome, and operculum. 



