Aperture not so much produced below; body whorl practically smooth 

 or with a row of tubercles above the middle 73. 



73. Body whorl practically smooth 



Lithasia obovata (Say) 

 Usually with a row of tubercles around the upper part of the body whorl 

 Lithasia geniculata Haldeman 



74. Columellar area of aperture smooth (Very many intergrading species, 



of which one representative is given here) 

 Goniobasis virginica (Gmelin) 

 Columellar area of aperture folded or twisted (Many intergrading spC' 

 cies, of which two representatives are given here) 75. 



75. Body whorl considerably lengthened; sides of body whorl usually almost 



parallel; outer lip almost perpendicular; operculum small and trans' 

 parent, with the spiral lines touching the margin at the base 

 Pleurocera (Strephobasis) curtum (Haldeman) 

 Sides of body whorl usually diverging; outer lip more oblique; operculum 

 more solid, with the spiral lines touching the margin at the left side 

 Pleurocera acuta Raf . 



76. Shell rather solid; spire usually slightly shorter than the aperture; colu' 



mellar area of aperture thickened 77. 



Shell usually thinner; spire usually slightly to decidedly longer than the 



aperture; columellar area thin 82. 



77. Shell wider than high; umbilicus wide; southwestern states 



Cochlwpa riograndensis P. & F. 

 Shell slightly higher than wide 78. 



78. Umbilicus oval and deep; Alabama 



Clappia clappi Walker Clapp's Shell 

 Umbilicus narrow or absent 79. 



79. Edge of aperture continuously in one plane; sutures slightly impressed; 



southeastern states 



Gillia altihs (Lea) Gilly 

 Lip projecting forward; sutures well impressed 80. 



80. Lip projecting centrally; shell solid; West Coast 



Fluminicola nuttalhana (Lea) Flood Shell 

 Lip projecting above; shell slightly thinner; central and southern states 

 — Globe Shells 81. 



81. With a narrow umbilicus; getting to be over %" 



Somatogyrus subglobosus (Say) 

 (Birgella subglobosa (Say) ) 

 Shell scarcely or not perforated; less than %" 

 Somatogyrus depressus (Tryon) 



82. Shell lengthwise ribbed ; western states 



Tryonia clathrata Stimpson 

 Not so 83. 



83. Whorls keeled or angulated above; west and south 84. 

 Whorls more rounded; more generally distributed 86. 



123 



