Genera Wrongly Referred to Planorbidae 203 



norbidae, which are unknown in both the Carboniferous (Mississippian 

 and Pennsylvanian) and Permian periods of America. The generic name 

 does not appear, as far as known to the writer, in any American work on 

 fossil puhnonates. It is j^robable that some Planorbidae will eventually 

 be found in Palaeozoic strata, since the family is so well developed in 

 Mesozoic time. 



