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 



