66 
PROCEEDINGS OF SOCIETIES. 
besides, it is not every young collector who possesses a copy of Messrs. Forbes 
and Hanley’s expensive work. The portion about dredging is a recapitula¬ 
tion of instructions -I have personally received from Dr. Ball, no mean autho¬ 
rity on this subject; and I need hardly add that the same instructions will apply 
whether the naturalist be collecting mollusca or any other marine animals for 
aquariums. I have endeavoured to be as brief as possible, and hope, in my 
endeavour to do so, I have not become unnecessarily obscure. 
COLLECTING. 
The first animals that appear in a list of British mollusca are the Acephala 
tunicata. If, when walking upon the sea-shore, about low-water mark, we turn 
over large stones, or look under the projecting eaves of rocks, we are almost sure to 
find some translucent, jelly-like masses, of various hues of orange, purple, yellow, 
blue, gray, and green—sometimes nearly uniform in tint, sometimes beautifully 
variegated, and very frequently pencilled as with stars of gorgeous device—now 
encrusting the surface of the rock, now depending from it in icicle-like projections— 
these are the Botryllidte, or true compound Ascideans, the first family of the 
Tunicata. They are also found attached to the stalks of sea-weeds. The Claveli- 
nidte, or social Ascideans, will be found attached to rocks, stones, and sea-weeds; 
and the Ascidiadse, or simple Ascideans, are taken in quantities, in dredging, attached 
to shells, and pieces of rocks; the Peloniadse are also taken in the same situations; 
while the last family—namely, the Salpidee—are free, and habitually swim in the 
waters of the ocean. Having thus briefly pointed out the localities where the 
Acephala tunicata may be expected to be found, we shall proceed at once to the 
more important part of this chapter—the collecting of the testaceous mollusca. 
The division of the testaceous mollusca into marine, land, fresh-water, and fluvia- 
tile, will, I think, be the most convenient to adopt—as, if we take them in the 
natural order of their affinities, we would have, on more than one occasion, to 
leave our station on the sea-side, or, perhaps, many miles from land, to seek some 
inland lake or stream. As the mollusca are arranged in the accompanying list in 
their proper order, this departure from it here will be of less importance. To 
begin, then, with the marine mollusca. Messrs. Forbes and Hanley speak of 
zones or depths of growth, and mean by this phrase the several belts or spaces mar¬ 
gining the land, or occupying the floor of the sea, distinguished from each other 
by the presence of peculiar features dependent on arrangements of their animal and 
vegetable inhabitants. 
The highest of these belts is the space between tide-marks, an interval of very 
great importance in the marine fauna of our islands. It is termed the Littoral 
Zone. Its features vary with the geological, or, rather, mineralogical characters 
of the coast, and its population—both as to kind and number—varies correspon¬ 
dency. Where it is rocky, it is inhabited by numerous gasteropodous mollusks ; 
where muddy or sandy, by burrowing bivalves; or in such localities it is not unfre- 
quently devoid of Testacea. The common limpets ( Patella vulgata ), the various 
species of periwinkles ( Littorina ), the dog-whelk ( Purpura lapillus ), certain forms 
of Trochus and Rissoa , the little Skenea planorbis , the common mussel, and the 
minute Kellia rubra , inhabit this zone on hard, rocky ground. On sandy and 
muddy shores, numerous bivalves are often thrown up by the waves, not a few of 
which are to be found alive in the lower division of this zone. In places where the 
water is brackish, it swarms with Rissoa ulvce. 
It is capable of being divided into several sub-regions, each marked by prevailing 
forms of animals. The uppermost is distinguished by the presence of the smaller 
varieties of Littorina rudis and L. neritoides; a second belt, by the abundance of 
Mytilus edulis , and the larger forms of Littorina rudis ; a third, by the preva¬ 
lence of Littorina littorea and Purpura lapillus ; a fourth and lowermost, by the 
dominance of Littorina littoralis , various Rissoce , especially R. parva and Trochus 
cinerarius These divisions into sub-regions will not, I think, be found carried 
fully out by the practical malacologist, for he will most generally find all the 
characteristic mollusca of the four regions in a space intermediate between the 
second and third. On some shores it is possible these distinctions may be traced. 
A second region is the Circum-littoral or Laminarian Zone, so called from 
