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 CRUSTACEANS appendages that precede the pleon. Byerley speaks of Limnoria lignorutn (J. Rathke), the gribble, under the later and now discarded name L. terebrans, and says that ' the wooden piles of the Rock lighthouse are completely drilled by this species.' ^ Mr. Andrew Scott, discussing surface collections in the vicinity of the Lancashire coast, says ' On a warm day, when the sea is calm, numbers of Eurydice may be seen disporting themselves on the surface. In their movements they are not unlike the " whirligig " beetle of the freshwater- ponds.'^ The species is not specified, but probably Eurydice achata (Slabber), often called E. pulchra (Leach), was the one observed. It is a curious cir- cumstance that dead specimens of this family when put into liquid often display the same whirligig movements as those executed by the live animals, from which it may be inferred that, when the creature is introduced to the surface film of the water, the structure of its body has something to do with the mode of motion independently of its will. Mr. A. O. Walker mentions Sphceroma serratum (Fabricius) from the stomach of a cod at Piel Island, and from that of a whiting at Morecambe, and Idotea marina (Linn.), also from a whiting at Morecambe. Though it does not seem to be specially recorded, the occurrence of Hemiartbrus abdominalis (Kroyer), so commonly parasitic beneath the pleon of Pandalus montagui, may almost be taken for granted. Of terrestrial Isopoda, or woodlice, strange to say, I have only found a single record, that of Oniscus murarius, another name for the very common O. asellus (Linn.), which Byerley oddly includes among the ' Myriopoda,' with the unimpeachable comment that it is ' very abundant about walls, rubbish, and damp localities.' * The Amphipoda are associated with the Isopoda in classification on account of certain obvious points of resemblance. The two sub-orders, besides being alike edriophthalmous or sessile-eyed, agree also in the distinctly tri-partite arrangement of the body. The consolidation of head and trunk which prevails in crabs and lobsters here gives place to a severance of the cephalic division from a seven-segmented middle body or person. The Sympoda make an approach to this arrangement by having five segments between the head and tail uncovered by the carapace. It is these five segments which throughout the Malacostraca must be considered as normally leg-bearing segments. But in the Isopoda and Amphipoda the two pre- ceding segments also carry legs, instead of having their appendages, as generally elsewhere, converted into mouth-organs. In some respects, however, the Amphipoda differ greatly from the Isopoda. They are usually com- pressed from side to side instead of being dorso-ventrally depressed. The appendages of the pleon are three pairs of pleopods with rami, as a rule flexible and many jointed, and three pairs of uropods with inflexible rami, not many jointed. In the Isopoda there are five pairs of pleopods and one pair of uropods, the flexible many-jointed condition being found only in the uropods, and there as an anomalous character. Above all, the Amphipoda are distinguished by the simple, or comparatively simple, branchial vesicles attached to some limbs of the person, and by the forward position of the heart, in contrast to the Isopoda, among which the heart (except in the anomalous group) is carried towards the rear in connection with the branchial system of the pleopods. When diligently searched 1 Fauna of Liverpool, 56. 2 7>a»/. Liverp. Biol. Soc. viii. 96 (1899). * Fauna of Liverpool, 1 1 1, 165