22 STROBILOPS, CANADA AND UNITED STATES. 



Geol. and Nat. Res. Indiana, 1902, p. 585 (near Cannelton, 

 Perry Co. ; New Harmonj^, Posey Co. ; Princeton, Gibson Co. ; 

 Wyandotte, Crawford Co., and Lake Maxinkuckee, Marshall 

 Co.; beneath logs and rubbish in ravines and moist places). 



Many of the older references to Helix or Strohila laby- 

 rinthica have been omitted, as it is impossible to tell whether 

 they refer to this species, ;S^. affinis or 8. cenea. 



The back, eye-stalks and tentacles are blackish gray, darker 

 streaks running from the collar to the eye-stalks ; sides of the 

 foot and the tail are clear whitish gray (PI. 4, figs. 9, 11). 



S. lahyrinthica differs from S. affinis by the longer, more 

 conspicuously unequal basal folds, the first (inner) two much 

 larger than the others, and the series does not form an even 

 curve as in affitiis; the infraparietal lamella generally emerges 

 more; the shell is smaller and generally less elevated, the 

 spire with more strongly convex outlines. In ;S^. miea the 

 whole shell, and especially the last whorl, is lower, the out- 

 lines of the. spire are less convex ; the basal folds are less 

 numerous, and there are none above the periphery; the color 

 is brighter and more transparent than in S. lahyrinthica. 



No locality was mentioned by Say, but his cotypes, four 

 specimens, are labelled "Penna. ; Hyde and Mason," and 

 probably came from the immediate vicinity of Philadelphia, 

 which place I have selected as type locality. One of these 

 shells is drawn in PI. 1, figs. 3, 4. 



Its usual stations are "under loose bark of logs, in half- 

 decayed wood, among dead leaves and in sod at bases of 

 trees. ' ' 



The umbilicus may be narrow, enlarging but little in the 

 last whorl, or it may enlarge to double the fonner -uddth in 

 the last half-whorl. The infraparietal lamella emerges more 

 or less conspicuously. The degree of angulation at the peri- 

 phery varies somewhat, and the sculpture of the base is also 

 variable, often nearly smooth in front of the aperture as in 

 the type, but sometimes distinctly ribbed throughout (the ribs 

 are represented somewhat too strong in PI. 1, fig. 8). The 

 parietal lameUa in rare instances penetrates as much as three- 



