19 



Synopsis Fresh-Water Moelusca 



Key to the subgenera of Feirissia. 



Shell elevated, apex radially striate Ferrissia s. s 



Shell depressed, apex smooth Lcevapex 



Subgenus FERRISSIA s. s. 



Shell conic, elevated, apex radially striate. 



Type: Ancylns rivularis Say, fig. 55. Radula, fig. 

 56. 



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I^ig- 55 



— — — — • • u^ia^ 



Fig. 56 



Subgenus L.EVAPEX Walker, 1903. 



Shell more or less depressed, apex smooth. 

 Type : Ancylns fiisciis C. B. Ads., fig. 57. 

 Radula: ferrissia diaphana (Hald.), fig. 58. 



Fig. 58 



Fig. 



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Genus GUNDLACHIA Pfeiffer, 1849. 



Shell small, thin, ancyliform, obliquely conical; apex posterior, excentric, 

 smooth or radially striate, inclined to the right ; basal side more or less closed 

 by a flat, horizontal septum ; aperture broad-oval ; margin continuous, simple, 

 entire. Animal as in Ferrissia. Radula with a bicuspid central and tricus- 

 pid laterals and marginals, the cusps short and broad. 



Key to the subgenera of Gimdlachia. 



Apex smooth or concentrically wrinkled Gimdlachia s. s. 



Apex radially striate Kincaidella. 



