6 LAND AND FRESH WATER MOLLUSKS 



TABLE I. DISTRIBUTION OF FRESH WATER SHELLS NORTH 

 OF LATITUDE 49°, ACCORDING TO THE DRAINAGE 



SYSTEMS NOW EXISTING. — Continued. 



Name of Species. 



Margaritana var. falcata , 



Unio complanatus , 



Quadrula plicata , 



Quadrula undulata 



Quadrula heros 



Quadrula lachrymosa .... 



Quadrula rubiginosa , 



Sphser 



Sphseri 



Sphser 



Sphaer 



Sphser 



Sphser: 



Sphser: 



Sphser: 



Sphser 



Sphser: 



Sphseri 



Sphser 



Sphser: 



Sphser 



Sphser 



Sphser 



Sphser 



Sphser 



Sphser 



ium simile 



ium striatinum 



ium solidulum 



ium stramineum 



ium rhomboideum 



ium walkeri 



ium fabale 



ium occidentale 



ium patella 



ium emarginatum 



ium tumidum 



ium spokani 



ium raymondi , 



ium partumeium 



ium jayanum , 



ium tenue 



ium transversum 



ium truncatum , 



ium lenticulum 



Corneocyclas virginica 



Corneocyclas idahoensis .... 



Corneocyclas scutellata , 



Corneocyclas sequilateralis . 

 Corneocyclas compressa .... 



Corneocyclas variabilis 



Corneocyclas abdita 



Corneocyclas ventricosa .... 



Corneocyclas rotundata 



Corneocyclas steenbuchi.... 

 Corneocyclas occidentalis... 

 Corneocyclas ultramontana. 



Corneocyclas arctica 



Corneocyclas nivalis 



Corneocyclas glacialis 



Corneocyclas pulchella 



Corneocyclas henslowana ... 



o o 



o 



o o 



o 



o o 



o o 



o o 



o o 



o o 



o o 



o o 



o o 



o o 



o» 



