Synopsis Fresh-Water Mollusca 



19 



Key to the subgenera of Fcrrissia. 



Shell elevated, apex radially striate Fcrrissia s. s. 



Shell depressed, apex smooth Lccvapex. 



Subgenus FERRISSIA s. s. 



Shell conic, elevated, apex radially striate. 



Type: Ancyliis rividaris Say, fig. 55. Radula, fig. 

 56. 



Fig- 55 



fv-'T^ S^w^hnjTj^ f^T-?*!! " 1^ "^ -y "(^x) "inj yu y y y ■.■■." j^i .■'-•' y "m u-j -y y - ji 



Fig- 56 



Subgenus L^^^VAPEX Walker, 1903. 



Shell more or less depressed, apex smooth. 

 Type : Ancyliis fusciis C. B. Ads., fig. 57. 

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



Fig. 58 



Fig. 57 



/^(jiLG^ 



Genus GUNDLAOHIA 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 Fcrrissia. Radula with a bicuspid central and tricus- 

 pid laterals and marginals, the cusps short and broad. 



Key to the subgenera of Gundlachia. 



Apex smooth or concentrically wrinkled Gundlachia s. s. 



Apex radially striate Kincaidella. 



