MICHIGAN ACADEMY OF SCIENCE. 139 



37. Aperture rounded-oval and almost circular, s^hell /fk^^^ 



white Pupoides. i (^^ -^-'^^ ^^ *-i 



P raarginatus (Say) X4. 



Aperture wider than high, shell dark chest- 

 nut Pupilla. 



p. nui^coiun'i (L ) X5. 



38. No teeth on columellar wall 39 



One or more teeth on columellar ^ v^P^-*^ 



wall Bifidaria . 



-4—* 



B. tappaiiiana (C. B. Adam?) x9 



39. Shell minute, altitude about 2 mm., color 



white Carychium. (c~\\ 



Shell larger, altitude about 4 mm., color dark chest- 

 nut 37 C ex.-guum (Say) X8. 



40. Shell small, altitude not over 7 mm 27 



Shell large, altitude over 12 mm 41 



41. Aperture produced into a canal in front, whorls 



flattened Pleurocera. t^iBtmi 



p. elevatuni (Say) xi. 



Aperture merely angulated in front with no canal. ^^^^^^ 



whorls more convex Gotiiabasis. \^^^^^^^ 



G. livescens (Meiike) XI • 



42. Shell with cap at end, nucleus almost 

 central Gundhichia. I" -x>*i^w,v«-.jr> 



G. stimp^oniana (Smith) Xo. 



Shell simple conical, nucleus at left 



of center Ancylus. m^^m Tfrntmr/i 



A. kirklandi (Walker) X5. 



