LITTORINA. 343 
The L. rudis, L. tenebrosa, L. zonaria and L. rudissima are 
usually inhabitants of the estuaries and muddy oozes, and 
rarely exposed to the full action of an open sea. 
We earnestly recommend naturalists, in their respective 
localities, to consign the four species above-named to basins of 
water, together with all the dwarf varieties inhabiting the 
crevices of rocks, when they will at once perceive that they 
are all identical with the type L. rudis; it will afford a 
practical proof that species founded on the characters of 
the shells are artificial and delusive, and that the soft parts 
must also be considered to obtaim specific distinction. 
The L. rudis, and all the varieties, are extremely impatient 
of continued immersion in water; when deposited in basins, 
the first object is to escape therefrom, and attach themselves 
to a dry spot. In estuaries, where they are often affused by 
the fresh water, they become, particularly the L. tenebrosa, 
thin and depauperated in their shells; they are sometimes 
for weeks deprived of even being sprinkled by sea-water. 
Though decided Pectinibranchiata, they live in the open air 
with nearly equal facility as the Pulmonifera ; and in reference 
to this fact, as regards another family, the Conovulide, there 
are still malacologists, who, notwithstanding the valuable 
observations of the Rev. T. Lowe and M. J. Berkeley, are not 
quite satisfied that they are pulmoniferous ; we have ourselves 
attempted to corroborate these views, in our remarks on the 
Pyramidellide. 
The L. littorea is the only species of this particular form 
that requires, to attain full growth, a regular bi-hodiernal 
immersion in sea-water, and to obtain it, the bulk of that spe- 
cies live in the lower littoral levels ; if they are deprived of it, 
they become stunted and dwarf. 
That variety of the LZ. rudis which is undoubtedly the LZ. ju- 
gosa of Montagu, varies from quite smooth to highly striated, 
and has even, ridged, reflected, spiral volutions, as repre- 
sented in the figure of Montagu’s ‘'Testacea Britannica ;’ it 
clothes the interstices of rocks on the Devon coasts in myriads. 
They are rarely or never immersed, as they dwell in the 
highest levels, in most exposed situations; im like manner 
