120 ST. H E L E N A ,
guislied by its size, being the largest of all the species. I t is still
found alive in considerable numbers, feeding upon the cabbage trees,
tree ferns, and native vegetation generally in the damp, cool
region on the high central ridge, at an altitude of 2600 feet above
the sea.
Zonites, Gray.
Z . c e l l a r iu s , Miill.—This native of the British Isles has
probably been introduced through the agency of the earth contained
in Ward s cases of plants. I t is easily recognised, being a small,
flat, spirally-formed snail, very abundant in gardens, where it assists
the common garden snail with its voracious aptitude for the destruction
of young vegetation.
Z . a l l i a r i u s , Miller.—Another British species, found commonly
associated with the other.
Helix, Linn.
H . a s p e r s a , Miill.-—This world-wide distributed creature, the
Common Garden Snail, is abundant all over the Island, and has,
without doubt, been introduced in the earth contained in Ward’s
cases of plants. I t exists in large numbers on thé somewhat barren
plains of Longwood and Prosperous Bay, where it finds a cool and
moist atmosphere as well as food amongst the creeping plants of
the Hottentot Fig (Mesembryanthemu,m édule). In the hot season,
when those plants partially die away, the empty snail-sheils may be
gathered from beneath them by hundreds.
* H . p o ly o d o n , G. B. Sow.=H. A l e x a n d r i , Forb.—A small
shell now found, together with the following five species, all of which
are natives of the Island, in a subfossil state, embedded in the
surface-soil on the north-eastern quarter of the Island, at an altitude
above the sea of 1200 to 1500 feet. Described and figured
“ Proceed. Geol. Soe.,” March 10, 1852, p. 198, pi. v. f. 9 ; also in
Mr. Darwin’s work on Yolcanic Islands.
*H . h e le n e n s i s , Forb.—A small, round, whitish-brown,
spirally-formed shell, of a Pacific type, from the roadside banks on
Side-Path above The Briars.
*H. e u t t e r i , Pfr.—A smaller species than the last, but found
associated with it.
*H. s p u r c a , G. B. Sow.—From near Flagstaff H ill; altitude
above the sea 1600 feet. Described in the appendix to Mr. Darwin’s