ZONITES. 29 



This species is unmistakable when the animal and its 

 shell have not parted company,, for the former is quite 

 black, which is not the case with any of the other Zo- 

 nites, being generally of a greyish colour ; the shell too 

 is of a deeper hue and much brighter. It is similar to 

 Z. excavatus, in having a large umbilicus, but the latter 

 has a number of longitudinal striae, which are not found 

 in nitidus. From what we have collected we should 

 consider them gregarious. About a quarter of an inch 

 in diameter. 



Hob. It chiefly inhabits marshy ground where it 

 may sometimes be found in great numbers, on the stems 

 of rushes and other aquatic plants, and on the tufts of 

 sedges which grow on the margin of ponds and streams. 

 It is pretty generally distributed, but somewhat local. 



Z. EXCAVATUS. Bean. PI. V, fig. 16. 



Shell depressed, small, shining, regularly striated, of a horn colour ; 

 umbilicus very capacious ; aperture orbicular lunate. 



Helix excavata, Alder, fyc. 



In form and appearance this shell comes nearest to 

 nitidus, but is of a lighter colour, has a larger umbili- 

 cus, and furnished with longitudinal striae, and not 

 nearly so lustrous. 



Hab. This species is the least common of the Zonites, 

 perhaps owing to the nature of the habitats which it 

 frequents ; these are chiefly the roots of plants in woods, 

 and beneath fallen stems and trunks of trees which have 

 been for some considerable time on the ground. It is 

 always found, as far as we have been able to judge, in 

 districts where the Carboniferous formation is prevalent. 

 We have found it in woods near Wakefield, and have 

 had specimens sent from near Dewsbury and Penketh, 

 all in such districts, and it has been discovered near 

 Newcastle and Scarbrough. It is, we think, an illustra- 

 tion of the fact that Geological formations have much to 

 do with the distribution of animal life, especially in its 

 lower developments, not so much certainly as climate, 

 yet more than has generally been admitted. 



