216 A NATURALIST IN THE GREAT LAKES REGION 



b 



FIG. 285. Land snails: a, Circinaria concava; b, Helicodiscus parallelus; 

 c, Omphalina fuliginosa; d, Polygyra tridentata; e, Zonitoides arbor etis; f, Polygyra 

 monodon; g, Pyramidula alternata; h, Philomycus carolinensis (a slug) ; i, Pyrami- 

 dula solitaria; j, P. perspeetiva; k, Succinea avara; I, S. ovalis; m, S. retusa; 

 n, Cochlicopa lubrica; o, Bifidaria armifera; p, Vertigo ovata; the last three much 

 enlarged, 



