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 A HISTORY OF LANCASHIRE these species : in tidal pools near Piel.'^ Discussing Cytheropteron humile (Brady and Norman) Mr. Scott writes : ' Many specimens of this remarkable little ostracod are found by washing water-logged and decayed wood in weak spirit, and examining the sediment. My father, who first found the species in material dredged in the Clyde, tells me that he always finds it when examining the sediment washed from old wood brought up in the trawl net, and remarks that it seems to be partial to that kind of habitat. In water-logged wood burrowed by wood-boring Crustacea, collected between tide marks in Barrow Channel, near Piel, April i8th, 1901.' The wood-boring Crustacea noticed in this passage would no doubt be the isopod Limnoria lignorum (J. Rathke) and the amphipod Chelura terebrans (Philippi). From the minute forms of the Ostracoda, self-contained in a kind of natural boxes which they are able to close tightly over all their appendages, we now pass to the much more showy Copepoda. These, however, attain to no majesty of size, and, except in some of the parasitic species, are as a rule diminutive. But there is a vast variety among them, sometimes great beauty of microscopic adornment, and no doubt some of the species attain to con- siderable economic importance by the dense masses of individuals with which they populate some waters. As to the strictly freshwater denizens of this county, it happens that the records are rather scanty, the attention of local investigators having been for the time principally fixed upon the marine fauna. The chief specialists on this group are not entirely unanimous as to the principles on which its internal classification should be based, and for the moment the lines which the leading authorities propose to follow are not completely mapped out. In arranging the order of our local species we are therefore unable to follow any single guide, but must be content with a systematic framework as harmonious as the indications already divulged allow us to make it. The family Calanidas has recently been much subdivided by Professor Sars. Accepted in the wider extension allowed it by Giesbrecht and Schmeil,* it supplies Lancashire with one of the smallest known Calanids, Paracalanus parvus (Claus), from the mussel beds at Piel,' and with Stephos gyrans (Giesbrecht), obtained by Mr. A. Scott 'amongst material collected in Laminaria bed, near Piel, at a very low ebb.'* Mr. I. C. Thompson speaks of '■ Pseudocalanus elongatus (Baird) ' as 'very common throughout the district, and seldom absent in any tow-net gathering.' ° The name should properly read Pseudocalanus elongatus (Boeck). It is right to mention that the late Mr. I. C. Thompson, F.L.S., applied himself with enthusiastic industry to investigating the marine Copepoda not only of this county but of all the neigh- bouring waters, and that his labours have been supplemented in the same productive field by a worthy coadjutor and successor, Mr. Andrew Scott, A.L.S. Among the numerous species brought to light by their researches I propose as a rule to introduce to the readers of this chapter only those which have been definitely assigned to Lancashire localities, with merely an occasional reference to those spoken of in general terms as belonging to the district. The family Diaptomidas, corresponding with the Centropagidae of Gies- brecht and Schmeil, may be credited here with at least four species, namely, Diaptomus castor (Jurine), of which ' Mr. Weightman met with specimens of 1 Op. cit. XV. 347 (1901). 2 Das Tterrelch, 'Copepoda Gymnoplea ' (1898). 170
 * Trans. Liverp. Biol. Soc. x. 127. * Op. cit. xv. 348 (1901). ^ Op. cit. vii. 181 (1893).