a4 THE MOLLUSCA OF THE FIRTH OF CLYDE. 
Cyclostrema serpuloides, Montagu. 
Helix serpuloides, Montagu; Turbo divisus, Adams (%) ; 
Rissoa divisa and Delphinoidea serpuloides, Brown ; 
Skenea divisa, Fleming. 
Habitat—Not uncommon in nullipore and shelly sand off 
Shellbole Bay, Cumbrae, and probably throughout the 
district, but I do not think I have ever taken it alive. Mr. 
Norman notes it as common in that part of Lamlash Bay, 
Arran, known as Landsborough’s Bay (probably dead shells 
only). 
British distribution —Throughout all our coasts from low 
tide to 25 fathoms (Brit. Con.) 
Foreign localities-—From southern Sweden throughout 
western Europe, the Mediterranean, and Adriatic. 
* Cyclostrema (Molleria) costulatum, M/dller. 
Habitat.—I obtained a single specimen, dead but perfect, 
off Silvercraigs, Loch Fyne, in 12 fathoms; nullipore. This 
species occurs in our post-tertiary formations, and the shell 
dredged by me had quite probably been washed out of one 
of these deposits. 
The distribution as at present known is entirely northern 
and Arctic; it has not been taken alive in British waters, 
excepting by Drs. Carpenter and Thomson, who dredged it 
in deepish water north of the Hebrides. 
Trocuus, Linné. 
Trochus helicinus, O. Fabricius. 
Turbo helicinus, Fabricius; Helix margarita, Laskey ; 
Turbo margarita, Fleming; Margarita vulgaris, Leach ; 
Margarita arctica, Gould (as of Leach). 
Habitat.—At low tide and down to a few fathoms on 
stones and seaweeds, common throughout the Firth. It is 
especially abundant at Farland Point, Cumbrae, where it 
may be got in great numbers and of good size on the 
under sides of loose stones at low tide. This and the 
next species belong to lLeach’s group or sub-genus 
Margarita. 
British distribution.—Chiefly northern, its range being 
from Shetland as far south as the Yorkshire coast on the 
east, and Dublin on the west, over all which district it is 
generally distributed and locally common, being perhaps 
most at home on the western shores of Scotland. 
