THE NATURAL HISTORY SURVEY. 185 



ribs; inferior margin with a large, well-developed median pro- 

 jection (Fig. 39, J). 



Radula formula: ^ + -f + 1 + i + f + -f + V (28-128); 

 central tooth with a base of attachment almost as wide as high, 

 much produced at the outer, lower corners; reflection tricuspid, 

 the central cusp very long, reaching below the edge of the base 

 of attachment, wide, the side cusps short and wide; lateral 

 teeth similar to central tooth, but the inner lower angle of the 

 base of attachment suppressed and the reflection bicuspid, the 

 inner cusp long, reaching below the base of attachment, and 

 the outer cusp short, but longer than in the central tooth; the 

 transition teeth similar to the laterals but the cusps shortening 

 and becoming more equal; marginal teeth narrow, long, bicus- 

 pid, the cusps of equal size. All of the teeth have well-devel- 

 oped cutting points (Fig. 39). There are about 80 rows of 

 teeth. 



Genitalia : Unknown. 



Distribution: Europe, Asia, United States south to Texas ; 

 Southern Canada and Alaska. Palaearctic. 



Geological distribution: Pleistocene; Loess. 



Habitat: Found associated with Zonitoides arboreus, Punc- 

 tum pygmceum, Bifidaria curvidens, etc., under stones and sticks, 

 in old and rotting logs. It requires a moist locality. 



Remarks: This is one of our most common mollusks. The 

 specimens from this region are very constant, exhibiting little 

 or no variation, and may be easily known by their rounded 

 spires and closely coiled whorls. The animal is rather shy and 

 crawls about with a wabbly motion as though the shell were 

 too heavy for it. The writer has found it particularly abundant 

 in the woods about Bowmanville, under and crawling over 

 chips and fallen pieces of bark. Prof. Pilsbry has shown* that 

 there are two species of Conulus which are generally mixed 

 together, viz., the present species and C. chersinus Say, which 

 is a shell with a much more turreted spire and more closely 

 coiled whorls. The teeth of the two species are widely differ- 

 ent, the present species having the formula 28-1-28 (original), 

 30-1-30 Binney, while chersinus has 18-1-18 according to Morse. 

 I feel certain that Morse had chersinus when he examined the 

 dentition, for the reason that a number of personal examina- 

 tions of undoubted fulvus all gave 28-1-28. The present 

 species is found throughout the area. 



*The Nautilus, Vol. XII, p. 113. 



