228 Trof. Dr. Fr. Vejdovsky on 



pigment, which in no way possess the characters of the genus 

 Niphargufi, but are representatives of a new genus inter- 

 mediate between Crangonyx and Gammarus, which I 

 designate Bathyonyx. To the species I give the name of 

 B. de Vismesi, gen. nov., sp. n., in honour of the discoverer. 

 Generic and specific characters : — Bathyonyx loith both 

 pairs of antennce very short {the jlagellum of the first usually 

 6-jointed, that of the seconds-jointed), loith 2-jointed secondary 

 branch on the first antennce. Eyes consisting of crystalline 

 cones diffusely distributed in the pigment. Gnathopoda with 

 weakly developed hands ; the hands of the anterior gnathopods 

 broader than those of the second pair. Telson split for two- 

 thirds of its length, coyisequently bilobed. Third pxir of uro- 

 pods with an outer 2-jointed, and a short inner l-Jointed 

 branch, scantily furnished loith setce, as in Crangonyx. Seg- 

 mental capsular epidermal sensory organs fusiform. 



Bathyonyx de Vismesi, gen. et sp. nn. 



The four specimens examined were all of equal length, 

 namely 3 mm., and of similar form. Being preserved in 

 formol they still showed traces of the original pale orange- 

 red coloration whicii was especially noticed by de Visraes 

 Kane in the living condition. 



The antennse are remarkably short, attaining about one- 

 fourth of the body-length ; there is no well-marked distinction 

 between the joints of the peduncle and the flagellum, for the 

 three basal joints pass gradually into those of the flagellum. 

 In this way the total number of joints of the first antennae 

 amounts to nine in two specimens and eight in the third. 

 (The fourth example was cut into serial sections.) The 

 third joint carries tlie 2-jointed secondary branch, of the 

 same form as in Niphargus for example, i. e. with an 

 elongated and greatly swollen basal joint, and a short and 

 slender distal joint (PL XI. fig. 2,n). The antennal setae 

 are weak, short, and scanty, from 1-4 on each joint as in 

 Niphargus. The sensory setse, which I have described from 

 the antennse of Crangonyx as sensory brushes [Sinnespinsel], 

 are also present in Bathyonyx, but they are very feebly 

 developed, so that they can be easily overlooked. 



These remarkable sense-hairs are characteristic not only of 

 these genera, but also oi Niphargus and Gammarus (especially 

 those of the first joint of the first anteunpe), occurring, in fact, 

 in the last-named genus in the greatest number. 



Thus in G. fiuviatilis from Herzegovina (collected by 

 Dr. Thon) I invariably found seven sensory brushes on the 



