HELICIDA. 27 
by no means common in England. Taylor records (Monograph, 
III, p. 246), that perforated rock dwellings are found in many 
places in Ireland, at Great Orme’s Head and Tenby in Wales, 
at Miller’s Dale, Derbyshire, at Whelpington, Northumber- 
land, “and probably at other places.” He observes (I, p. 312) 
that “the ability of the Helices, in course of ages to excavate 
these tunnels, can scarcely be questioned, as, in addition to 
their demonstrated power to abrade limestone and chalk with 
their odontophores, M. Bouchard-Chautereux has affirmed from 
actual experiment that their mucoid secretions exhibited a dis- 
tinctly acid reaction, testified by the reddening of litmus paper, 
and would, therefore, tend to dissolve the rock, and thus facili- 
tate the process of the excavation. Probably, however, the 
movements of the snails within the cavities have been a chief 
cause of their excavation, the wearing power of the friction of 
the foot being clearly demonstrated by the worn margins of 
the cavities, and by the sunken tracks leading thereto, worn 
away in the rocks by the passage to and fro of the countless 
generations of snails which have for untold ages sought their 
shelter.” 
Var. conoidea, Picard. 
General in hedges ; Cundall. 
Bratton St. Maur! Uncommon. 
Var. globosa, Moquin- Tandon. 
One example from a hedge near Pitcombe Rectory ! 
Var. tenuior, Shuttleworth. 
Bratton St. Maur! <A rare form usually occurring near 
the sea. 
Burnham ! 
Var. nigrescens, Moquin- Tandon (Plate tv, 1). 
Occasionally with the type in hedgebanks. 
Bratton St. Maur and Rimpton ! 
Miss F. M. Hele found a specimen at Burnham, which 
was “literally as black as ink.” 
Var. undulata, Moquin- Tandon. 
Holbrooke, near Wincanton ! 
Weston-super-Mare ; J. Madison. 
Bristol; Miss Hele. Figured in Taylor’s Monograph, 111, 
Pl. xxaTr, 
Var. flammeu, Picard. 
Not uncommon in the Wincanton district ! 
