A HISTORY OF KENT 



jointed. It is a smooth and shining, rapidly running species, common 

 at Tunbridge Wells, and probably all over England. Oniscus asellus, 

 Linn., agrees with it in the number of joints to the flagellum and in 

 being found at Tunbridge Wells and indiscriminately elsewhere, but it 

 is very much larger, slow-moving, and though glossy by no means 

 absolutely smooth. In all our remaining species the flagellum is 

 two-jointed, still in Platyarthrus hoffmannseggii, Brandt, the first of 

 the two joints is characteristic by its minuteness. This species has 

 been taken at Tunbridge Wells in an ants' nest, the habitat which it 

 appears invariably to occupy. Porcellio scaber, Latreille, is common at 

 Tunbridge Wells, but not a rarity anywhere. Of the same genus 

 P. pictus, Brandt and Ratzeburg, and P. laevis, Latreille, are also 

 assigned to this county.' Between the first and third no confusion is 

 possible, because P. scaber, as the name intimates, is rough all over 

 with tubercles, while the very broad P. laevis is named from the 

 smoothness of its surface. The painted Porcellio is recorded from 

 Chislehurst and has also been taken at Tunbridge Wells. It comes near 

 to P. scaber, but it differs from it in having the first joint of the 

 flagellum longer than the second. Also the head is very dull in contrast 

 to the variegated colouring in the rest of the dorsal surface. Metoponorthus 

 pruinosus, Brandt, is recorded from Chislehurst.'' It differs from the 

 species of Porcellio, which have the front strongly trilobed, by a 

 reduction of the lateral lobes giving it comparatively a ' straight front ' 

 in accord with its generic name. Cylisticus convexus (de Geer) is re- 

 ported by Mr. W. M. Webb from Bluebell Hill, Maidstone. It is Hke 

 Porcellio, but capable of globation.^ AnnadilUdiitni vulgare (Latreille) 

 and A. nasatum, Budde-Lund, have both been taken at Tunbridge Wells, 

 and the latter also at Riverhill, near Sevenoaks. From all the preced- 

 ing terrestrial isopods, except Cylisticus, they are marked off by the 

 power they possess of rolling up into a ball. In the common species 

 the front is simple, but in A. nasatum its middle part is turned back 

 dorsally with something of a nasiform projection. Though twelve out 

 of the twenty-four English species may be thought a fair proportion 

 for a single county to possess, no doubt Kent will eventually be found 

 to have several in addition to those here enumerated. 



The Amphipoda, which agree with the Isopoda in having sessile 

 eyes and a peraeon or middle body of seven articulated segments, differ 

 from them very essentially by the position of the breathing organs. 

 These in the genuine isopods are confined to the pleon, but in all the 

 amphipods are attached to limbs of the peraeon. Of this latter order 

 the species are extremely numerous, and it is reasonable to suppose that 

 the few recorded from Kentish waters are an inconsiderable percentage 

 of the number really present. The fresh-water species, Gammarus 

 pulex (Linn.), is plentiful here as elsewhere, found in ponds, rivulets, 

 and occasionally in wells. But of more interest are the 'well shrimps' 



' British sessile-eyed Crustacea, ii. 482, 484. ' Loc. cit. ii 488. 



3 The British Woodlice, p. 39, pi. 21. 



250 



