202 Mr. W. Thompson’s Catalogue of the Land and 
shire and Northumberland. Clausilia biplicata is confined to the 
south of England; C. Rolphii to one or two localities in the south- 
east; C. dubia is, I believe, as yet known only to the north of England. 
Limneus glutinosus, Cyclostoma elegans, and Cyclas rivicola, are some- 
what widely diffused in England, but are unknown to Scotland. 
Segmentina lineata is noticed by Mr. Gray as a south of England 
species, but is included in Mr. Forbes’s list of Scottish mollusca. 
The genus Unio, as now restricted, becomes rare towards the north 
of England, and is not found in Scotland. The species of land and 
freshwater mollusca indigenous to Ireland, assimilate with those of 
Scotland much more nearly than those of England. About one- 
half of the species in which Ireland is deficient prevail chiefly in the 
portion of England which lies to the south of Ireland. 
I should, perhaps, in conclusion, have ventured to offer some re~ 
marks on the causes which appear to influence the distribution of 
our Irish species, but the views put forward in my friend Mr. Forbes’s 
excellent ‘ Report of the Distribution of Pulmoniferous Mollusca in 
the British Isles,’ published in the volume for 1839 of the Report 
of the British Association for the Advancement of Science, renders 
unnecessary anything I could say upon the subject. 
APPENDIX. 
My notice of the genera Arion and Limaz at the beginning of this 
article is so scanty, that I here avail myself of very full and inter- 
esting observations on the species appertaining to them, since fa- 
voured me by Mr. Clarke, who much more than any one in this 
country has bestowed attention on the subject. 
Arion ater. 
A. Empiricorum, Férus., t. 2. 
La Bergerie, Queen’s county; county Galway. Too abundant in 
both places, varying from the light yellow-coloured variety through 
all the shades of brown or ochre to deep black. The brown variety 
seems to predominate in Killereran (county Galway) meadows and 
woods, but I have repeatedly observed the two colours indiscrimi- 
nately mixed together in precisely the same localities, both in fields 
and gardens. The yellow, which I have never taken of the full 
size, is mostly confined to the decaying pieces of wood found among 
damp moss. I have not noticed the variety with the scarlet foot, as 
in fig. 2. t.2. Fér. I have seen two individuals busily engaged de- 
vouring a snail (H. aspersa), both their heads being introduced 
within the shell: the snail appeared to be fresh killed. 
Arion hortensis. 
A. des Jardin, Férus., t. 2. f. 4—6. 
Var. a. f. 6. Fér. 
Var. (3. Pfeiffer. 
La Bergerie and county Galway. Bynomeansscarce. Férussac’s 
figures agree accurately with mine, but are represented of larger 
dimensions than any I have seen. I have taken the young of a 
very minute size with the orange foot, and the colours equally as 
