100 Natural History of theMountain of Montreal, 



nates, in about equal proportions, witli oblique, zigzag bars of 

 dark-brown ; the.se bars grow narrower and lighter on the lower 

 surface as they converge to the umbilicus; they are geneially in- 

 terrupted by a light coloured zone which issues from the middle 

 of the inner margin of the aperture ; whorls five to six, flattened 

 above, conspicuously plaited at the lines of growth, so as to pro- 

 duce a rough surface above, but nearly smooth beneath ; the shell 

 has a sharp dividing line between the upper and lower surfaces in 

 all its earlier stages, which disappears only at maturity, forming a 

 circular aperture, slightly modified by the preceding whorl ; lip 

 simple and delicate ; umbilicus large and deep, exhibiting all the 

 volutions. Diameter often an inch. 



''■'■ Animal whh the head and tentacula of a light slate color,, 

 back brown, remainder of the upper surface brownish orange; 

 eyes black ; base of foot drab coloured ; collar saffron. Tenta- 

 cula one third of an inch long, blackish at tip. Foot not much 

 exceeding the diameter of the shell, teraiinating in a broad, flat, 

 obtuse tip ; a light marginal line runs along the foot from the 

 head to the posterior tip." 



The habits of this species are similar to those of H. Albolahris' 



Fig. 6. 



Fiff. 6. — Helix Monodon. (Rackett.) 



The species represented by Fig. 6. — " the single-toothed snail^" 

 is much smaller than either of the other two, and not so abun- 

 dant. It has a sort of a tooth on the whorl just at the edge of 

 the aperture. The technical description is thus given. 



" Shell slightly convex ; whorls five or six, narrow, diminishing 

 very gradually in breadth from the outer whorl to the apex, mark- 

 ed by very fine lines of growth, and covered with a dark russet or 

 chesnut coloured epidermis, which is beset with very minute, hair- 

 like projections ; aperture contracted by a deep groove behind the 

 lip ; lip white, narrow, reflexed, a little grooved on its face, ex- 

 tending on the base to the umbilicus, and slightly contracting it, 

 and its outer edge not projecting beyond the surface of the whorl ; 

 umbilicus deep, not exhibiting all the volutions, partially cohered 

 by the lip ; base rounded, very much excavated at the umbilical 



