98 



GEOIvOGY OF LA SALLE COUNTY. 



dish Spots, some of them oblique, others runnin«- into 

 lines on last whirl, diameter nearly one inch. The 

 most abundant species in the county; live in colonies 

 of one hundred or more in some localities. Semi-fossil 

 in the Quaterary deposits. 



Helix altcrnata. Say, variety. — A sharply cari- 

 nated variety with coarse stria, resembling H. mor- 

 dax, Shutt. I believe the true mordax is from Ten- 

 nessee, and this differs in not having- as coarse striae. 

 A well marked variety. 



Helix solitaria, Say. — Shell coarse and heavy in 

 texture, has a broad umbilicus, is g-lobose, coarsely 

 and obliquely striate, whirls six, lip acute, has two 

 reddish revolving- bands; aperture circular, color 

 brownish; breadth one inch. Abundant in some local- 

 ities; also in the Quaternary, one of the lhree banded 

 species in the county. 



Helix striatella, Anthony. — Shell small and de- 

 pressed, whirls three and one-half with distinct 

 oblique striae; umbilicus largfe, lip acute, color brown- 

 ish or russet, breadth one-fourth inch. Quite abun- 

 dant. 



GENUS HELIX, LINN. — SUBGENUS MESODON, RAP. 



Helix albolabris, Say. — Shell has nearly six whirls 

 obliquely and finely striated, horn colored; lip white 

 inside and reflected; umbilicus covered by the peris- 

 tome greatest diameter thirty-two mill; abundant. 



This fine species is so distinct in its characters as 

 to be easily recog-nized. Some specimens have a tooth 

 on the parietal wall. 



Helix multilineata, Say. — Shell depressed and 

 sub-g-lobose, whirls nearly six, with fine oblique striae 

 aperture lunate, a little contracted by peristome; or- 

 natnented with numerous reddish bands and lines, per- 



