PLATE XCIX. 



HELIX CONTORTA. 



THICK RIVER CHEESE SHELL. 

 GENERIC CHARACTER, 



Aperture of the mouth contracted and lunulated. 



SPECIFIC CHARACTER 



AND 



SYNONYMS. 



Shell thick, umbilicated, flattish. Aperture narrow and crescent- 

 shaped. 

 Helix Contorta : testa subumbilicata plana utrinque asquali ; 



apertura lineari arcuata. Gmel. Linn. Si/st. Nat. 



p. 5624. 

 Planorbis minima crassa Tiney many-circled, thick, river cheese 



shell. Petiv. Gaz. tab. 92. fig. 8. 

 Planorbis minima crassa, utrinque umbilicata, anfractibus subde- 



pressis. Crassa. Da Costa Br. Conch, p. 66. 



sp. 37. Tab. 4. fig. l\. 



g 2 



