189 



spire, or convex, and can only be recognized with cer- 

 tainty by their round aperture and reflected lip, their 

 exterior never having tubercles or spines, and their pos- 

 sessing a horny operculum. 



Cyclostoma planorbula Cyclostoma fasciata 



volvulus mumia 



carinata quaternata 



sulcata ferruginea 



unicarinata decussata 



tricarinata lineolata 



obsoleta mammillaris 



rugosa ligata 



labeo lincinella 



interrupta orbella 



ambigua fimbriata 



semilabris multilabris 



flavula elegans. 



Doubtful Species. 

 Cyclostoma patulum Cyclostoma truncatulum. 



