PLATE IY. 



First Fresh-Water Formation, 



1. Cyclostoma mumia. 



2. Lymnceus strigosus. 



3. . . longiscatus. 



4. . . acuminatus. 



■ 



5. Planorbis lens. 



6. An articulated stem (with projecting papillae), resembling the root of 



an Equisetum. 



