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 Botryllidae, or true compound Ascideans, the first family of the 

 Tunicata. They are also found attached to the stalks of sea-weeds. The Claveli- 

 nidse, or social Ascideans, will be found attached to rocks, stones, and sea-weeds ; 

 and the Ascidiadae, 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 Salpidae 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- 

 dently. 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 



