64 THE NAUTILUS. 



wave (= muscle contraction) much shorter than the interval (in 

 space). 



Agriolimax agrestis (L.). 1 Three zones distinct, the median, 

 rather narrow, does not reach the anterior end, so the marginal is 

 continuous all around. Waves distinct, about 16 (in specimens 

 35 mm. long) in rapid succession. 



Arionidce. 



Arion rubellus |St. s A slightly and not sharply marked median 

 zone, wider towards the anterior end, somewhat hyaline, that is : 

 with few or none of the yellowish opaque (glandular?) granules dis- 

 seminated in the rest of the sole. Waves visible, but not distinctly, 

 more remote from the surface of the sole than in Polygyra and 

 Limax, and more remote from each other than in Agriolimax agrestis, 

 and proceeding slower. 



Pldlonaycidiz. 



Philomycus dorsalis (Binn.). No well marked zones, and no 

 waves seen. 



Helicida Polygyrina. 



Some additional PoJygyrce examined show essentially the same 

 features as those noted before ; all with distinct zones and waves. 



P. albolabris (Say). Foot and sole light-colored, not drab, and 

 color in the three zones little different ; waves about 12. 



P. multilineata (Say). Sole drab-colored ; waves 9-10. 



P. appressa (Say). Sole long and narrow; waves 10-11, com- 

 paratively numerous for the size of the snail. 



P. stenotrema (Fer.). Waves about 7. 



P. hirsuta (Say). Median zone grayish, marginal dull, pale red- 

 dish to purplish, with strongly marked transverse lines. Waves 

 about 7. 



Pupidtz. 



Bifidaria pentodon (Say). Foot very short ; zones not evident on 

 the sole ; waves distinct, about 3, extending over nearly the whole 

 width of the sole. 



1 From one place (in Lake Co., Ohio) several dozen were collected, showing 

 extremes of color: from whitish without any dark mottlings to almost entirely 

 black ; some of a tan to brownish tint. 



2 From a nursery in Lake Co., Ohio. Appears to be distinct from hortensis ; 

 described about 1682 ; European. 



