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A HISTORY OF STAFFORDSHIRE has a rougher surface. The flagellum or slender lash-like part of its second antennae is divided into only two joints instead of three, and the first two pairs of pleopods, appendages of the first and second pleon-segments, are furnished with pseudo-tracheae, aids to aerial respira- tion which are wanting in Oniscus. The third species of this tribe in Mr. Brown's catalogue should be called Armadillidium vulgare (Latreille). It belongs to a separate family, Armadilli- diidae. Its antennae and pleopods have the characters above mentioned as pertaining to P. scaber, but among marks distinguishing it from that species are the globular form into which the body can be composed, and the structure of the uropods or last pair of appendages, which have the outer branch laminar instead of cylindrical. The vernacular names, wood louse, scabrous wood louse or slater, and lesser pill millepede are of old standing and will not perhaps easily be dislodged, but they conceal the true position of these animals in the system of nature. By calling them woodland shrimps or garden shrimps we at least run a happy risk of bringing home to the unscientific understanding the fact that they are true crustaceans. The last of the three might better be called in English the pill shrimp than the pill millepede. It is pro- perly distinguished by Mr. Brown from Glomeris marginata, Olivier, the greater pill millepede, 14 which really is not a crustacean, but a species of the family Glomeridae, in the order Diplo- poda, among the myriapods. Armadillidium vulgare, with its modest supply of fourteen legs, has no claim to be noted as either a lesser or a greater member of that many-footed company. The sub-class Entomostraca, divided into three great sections, Branchiopoda, Ostracoda, Copepoda, does not display that arithmetical unity of body segmentation observable in the Malacostraca. On the contrary, the segments are sometimes many more than twenty-one, and sometimes are left almost entirely to the imagination. The family Argulidae, which Mr. Brown assigns to the Poecilopoda, as to an order of equal rank with the Entomostraca, is now generally grouped with the latter. Its peculiarities, however, still leave its exact status uncertain. Some authorities place it among the Branchiopoda, others among the Copepoda. In the former section it has to be distinguished from the Phyllopoda and Cladocera as an order Branchiura, or as a sub-order, if the Branchiopoda are themselves regarded as an order. The genus ArgultU) O. F. Mtlller, has the strange character that its second maxillae are metamor- phosed into sucker-disks, by which it can attach itself firmly to a fish, and also march freely over the surface of its victim by holding on with one sucker and moving the other alternately. These disks are a striking example of the adaptability with which crustacean appendages lend themselves to varying circumstances. The adhesive apparatus in the Argulidae, however, is not always or entirely dependent on the method of suction, but is always partially and sometimes wholly contrived by hook and by crook. In any case the adhesion is intended to subserve another kind of suction, effected by the siphon or mouth-tube, in the structure of which the lips, mandibles, and first maxillae take part. An unpaired venomous sting may or may not be present. Argulus foliaceus (Linn.), sometimes called the carp-louse, is a very indiscriminate feeder, attaching itself not only to carp and sticklebacks, but to several other freshwater fishes, and even to tadpoles. It is a powerful swimmer. If it is to be classed with the parasitic Copepoda, it markedly differs from that group in general in that the females do not carry their eggs about with them after extrusion, but deposit them on some extraneous substance. Records of Phyllopoda arc for the moment wanting in this county. The Cladocera have received more attention. For though Mr. Brown's examples are for the most part very vague, a welcome contribution to this branch of our subject was supplied in 1895 in the Synopsis of the British Cladocera 1 by Mr. T. V. Hodgson, a gentleman since distinguished as biologist to the National Antarctic Expedition on the 'Discovery.' In the same year was published the first part of a classical work on this group, entitled Revision des Cladaceres, by Jules Richard. 16 M. Richard defines the Cladocera as small free Entomostraca, with distinct head, the rest of the body usually compressed from side to side, and enclosed in a two-valved carapace ; the antennae of the second pair two-branched, each branch carrying setae, and composed of only two to four joints ; the mandibles altogether devoid of palps ; the pairs of feet four to six in number, of which usually the majority or all are foliaceous, lobate ; the eye single." 11 Nat. Hist. Tutbury, p. 137. 11 Jount. Birmingham Nat. Hist, and Phil. Soc. 101. , " Ann. Sci. Nat. Zoo/, (ser. 7), vol. xviii, p. 279, continued in (ser. 8) vol. ii, p. 187 (1896). " Op. cit. 304. I 3