ZONITES. 105 



epidermis rather thin ; whorls 5, convex, body whorl about 

 half the size of the shell ; spire somewhat produced, apex 

 obtuse ; suture deep ; mouth forming three-fourths of a circle ; 

 outer lip thin, somewhat oblique, reflected near the pillar ; 

 timbilicus narrow but deep. 



Inhabits moist places at the roots of grass, among 

 moss, and under stones throughout the British Isles. 

 This common species not only delights in damp situ- 

 ations, but is capable of remaining for some time 

 under water. On one occasion when in search of 

 Pisidia, having pulled up some aquatic plants, I 

 found among their roots several living specimens of 

 Z. nilidiis, which had been submerged to a depth of 

 six or eight inches. 



The chief points of difference between this and the 

 last species will be seen in the following table of 

 comparison : — 



Radiatulus. Nitidus. 



Tentacles^ upper pair very Tentacles thick. 



slender. [ 



Shell equally convex above Shell larger, much more con- 



and below, very glossy, t vex above than below, 



very thin. ! glossy, moderately thin. 



Strice less strongly defined. 

 Spire somewhat produced. 

 Suture deep. 

 Outer lip somewhat oblique. 



Var. albida. — Shell white or colourless. Dead specimens 

 found by Mr. Choules among the rejectamenta of the Thames 

 at Richmond, B.C. 



StricB strongly defined. 

 Spire slightly raised. 

 Suture not very deep. 

 Outer lip scarcely oblique. 



8. Z. excava'tus,* Bean. Pl. VII. 



" Body slender, greyish-white, with three or four raised lines 

 along the neck ; mantle closely covered with milk-white specks ; 



* Hollowed out (in reference to its wide and deep umbilicus). 



