29 

 SUBFAMILY PLANOIIBTN^. 



GK.A'US I»I.A.:>'<>KltIS, GUETTAKD. 



This is one of our most abundant mollusks, and may 

 |De found usually in quiet waters feeding on confer- 

 vaceous vegetation or decayed matter. The genus is 

 represented by a number of species in this county. Of 

 Planorbis, T believe that more sj^ecies have been uiadc 

 than will stand. We have several varieties of P. 

 trlmlvls that are very good an varieties, and I believe 

 as much entitled to the rank of distinct species as some 

 that are called such. 



l»f.A.^<>KI6IS <-I.AI5«.4riJS, Say. 

 Shell has live wliirls, rugose in appearance, spire 

 regular; umbilicus large, deeply concave ; exhibiting 

 the volutions; color browiiisli ; brfnidth nearly om* 

 inch. Loc. Fox lliver. 



SUBGENUS FLANORBELLA, Kalde. 



E-l.Ai^OKKIS « .VWB»A:MiI./VTI'.S Say. 



Shell has four wliiils ; umbilicus deep, color yellow- 

 ish horn ; apertures dialated, campanulated ; greatc^st 

 breadth one-half inch. Abundant. 



SUBGEUNS HELISOMA, Swaixsox. 



l»I.y».:\OS«i8I« TKIVOI.VIS, SAy. 



Shell lias four whirls, which are iinely striated ; two 

 and a half whirls visible upon tlu^ right side, the ante- 

 penultimate disappearing within the umbilical cavity : 

 aperture large, slightly thickened within the margin. 



