"281) W. SAVILLE-KEXT, COXTRIBUTIOXS TO A 



scribed by the above-named authority. The granular character 

 of the cuticle in conjunction with the impressed dorsal area i> 

 suggestive of an atfinity with Arrhenurus^ while the character of 

 the palpi and genital plates more nearly approaches Liinnesia. 



Genus 5. Liinnesia Koch. 



Body symmetrically ovate, inflated : cuticle soft and pliant : 

 :short isolated glandular setae scattered sparsely over the cuti- 

 cular surface, one pair of setae upon the anterior border of the 

 body of larger size and presenting an antenniform aspect ; epi- 

 mera forming four distinct groups, the two anterior and the two 

 posterior pairs on either side being respectively adnate, the 

 epimera of the fourth pair of legs constituting a triangle, the 

 base resting upon the antecedent epimera and its apex giving 

 attachment to its decussating limb ; the two posterior legs bear- 

 ing fascicles of swimming-hairs, the last joint of the fourth pair 

 having a simple aciculate termination ; palpi subulate, setiferous, 

 each second joint with a simple tooth-like projection developed 

 on its under-side; genital plates evenly ovate or elliptical, 

 each with three lineally disposed ovate acetabula ; eyes forming 

 two distinct pairs ; ova deposited loosely within a common 

 areolated matrix ; larvae hexapod, sparsely hirsute, with two 

 shorter antero- and four long postero-marginal setae ; non- 

 parasitic (?) ; nymph resembling the adult, but the genital plates 

 bearing respectivel}^ but two acetabula. Type : Liinnesia 

 histrionica Herm. sp. 



The characters afforded by the genital plates, combined with 

 those of the epimera and the clawless terminations of the two 

 posterior legs, renders Liinnesia one of the most distinctly defined 

 generic groups of the Hydrachnidae. The type-form of the genus, 

 synonymous with the Hydrachmi histrionica of Hermann, Atax 

 histrionus of Duges, and Limnesiafidgida of C. L, Koch, is among 

 the most abundant species in the neighbourhood of London, 

 and has been specially selected by the writer for working out 

 the anatomical features of the group. The ova and larvae of 

 this species have been investigated, and likewise the nymph 

 coadition, hitherto unrecognised, but which has been found to 

 he identical with the so-called lAmnesia cyanipes of C. L. Koch, 



