CRUSTACEANS 



figure and describe the species under a new one, Cancer Astacus tnultipes. 

 He says ' By means of the accurate pencil of Mr. Henry Boys, who 

 favoured me with drawings of many of the marine animals found at 

 Sandwich, I have been able to identify this crab as an inhabitant also of 

 the Kentish coast.' ^ The genus Macromysis, White, to which this 

 species is often referred, is much later than Leach's Pr annus. 



To the sessile-eyed Malacostraca of this county no great attention 

 has hitherto been paid. T^he Handbook to Dover incidentally mentions 

 a single isopod, saying in regard to Leander serratus, ' Oftentimes the 

 carapace is disfigured by the internal parasite, Bopyrus squillarum, scarcely 

 a specimen being free from it, but in the last two years they appear to 

 have escaped.' Strictly speaking, this is not an internal parasite. In 

 the proper sense of the word, one might say, it is not a parasite at all. 

 The animal insinuating itself between the side wall of the prawn's 

 carapace and its branchiae lodges there, apparently without doing its 

 host any damage whatever unless by wounding its vanity. But if the 

 prawn suffers from the look of having a swollen cheek, the female 

 Bopyrus endures more injury than she inflicts. In her narrow apart- 

 ment she becomes quite lopsided and foregoes all independence of 

 movement for the sake of the very numerous progeny which she 

 brings into the world. Her mate is by comparison insigni- 

 ficant in size, but he retains his symmetry and a limited pedestrianism. 

 Giard and Bonnier have pointed out that Latreille, to whom the generic 

 and specific names of Bopyrus squillarum are due, did not distinguish 

 L. serratus from L. squilla. They therefore propose the name B. 

 fougerouxi for the species of Bopyrus which is found in the former. 



Of all the free-swimming marine Isopods I find none mentioned 

 except Sphaeroma serratum (Fabricius) as to which Leach says, ' This 

 species is very common on the rocky shores of Devonshire, Kent, and 

 Cornwall.' ' As the generic name implies, these creatures can roll 

 themselves up into spheres like some of the land isopods. 



The freshwater isopod of England is Asellus aquaticus (Linn.). It 

 is abundant in little weedy streams about Tunbridge Wells and not 

 likely to be scarce in any county. 



The Isopoda terrestria are at present less meagrely represented than 

 the aquatic families, though adequate research would be sure to invert 

 this numerical relation. Lugia oceanica (Linn.) has been observed at 

 Dover and other places on the coast of Kent by Messrs. W. M. Webb 

 and J. A. Murie. This is a land species never found except at the lip 

 of the sea."" Trkhoniscus pusillus, Brandt, is recorded from Chislehurst 

 by Bate and Westwood,* under the name Philougria riparia (Koch). 

 From the following species of the group it may be briefly distinguished 

 as alone having a four-jointed flagellum on the peduncle of the 

 second antennae. Philoscia muscorum (Scopoli) has this flagellum three- 



' Trans. Linn. Soc. London, ix. 91 (1808). = Ibid. xi. 363 (18 15). 



3 W. M. Webb and C. Sillem, The British Woodlice, p. 20, pi. I (1906). 



* British sessiU-eyei Crustacea, ii. 457. 

 I 249 i'Z 



