PLANORBIS. 263 



Sub-gen. anisus, Fitzinger (Trophidiscus, Stein). 



Shell greatly depressed ; whorls very numerous, periphery 

 keeled. 



carinatus, Mull. ruarnioratus, Mich. 



depressinius, Moric. subangulatus, Phil. 



dubius, Hartm. subcarinatus, Charp. 



kermatoides, D'Orb. submarginatus, Crist, and Jan. 



marginatus, Drap. vortex, Linn. 



Sub-gen. spirorbis, Svvaiuson. 



Shell much depressed ; whorls many, periphery simple. 



acies, Porro. nitidulus, Dkr. 



auatinus, D'Orb. placentula, Kryn. 



angulatus, Chitty. Kedfieldi, C. B. Adams. 



catillus, Anton. Reveutlowii, Beck. 



contortus, Linn. septemgyratus, Ziegl. 



fusculus, Parr. Sibiricus, Dkr. 



leucostoma, Mich. spirorbis, Mull. 



luridus, Pfeiff. tseniatus, Morel. 



Mac Nabiauus, C. B. Adams. virens, C. B. Adams. 

 magnificus, Conr. 



Sub-gen. nautilina, Stein. (? Gyraulus, Agassiz) 



Sbell orbicular above, flat beneath ; whorls few, rapidly 

 increasing. 



albus, Mull. circumlineatus, Shuttl. 



ammoneus, Beck. compressus, Ilutt. 



arcticus, Beck. cleflectus, Say. 



Brondelii, Raym. deformis, Lam. 



Chiuensis, Dkr. dilatatus, Gould. 



