NIPHARGUS. 311 



I M PHI POD. I GA M MA RIDES. 



NATATORIA. 



Genus NIPHARGUS. 



Nipkargus. Schiodte, Act. Soc. Reg. Dan. 1851, p. 26. Trans. Ent. 



Soc. Loncl. 2 ser. v. i. p. 149. Nat. Hist. Review, i. 



p. 43. White, Hist. Brit. Crust, p. 186. Spence 



Bate, Cat. Amph. Brit. Mus. p. 174. 

 Gammarus part. Koch, Crust. Myr. u. Arach. Deutschl. h. 5 and 36. 



Costa, Mem. d. reale Accad. d. Sci. Napoli. 1. 



Generic character. Animal slender. Eyes obsolete or rudi- 

 mentary. Superior antennae having a secondary appendage. 

 Inferior antennae shorter than the superior. Gnathopoda 

 uniform, chelate or subchelate. Posterior pair of pleopoda 

 biramous ; one ramus rudimentary, the other very long and 

 double-jointed. Telson single, deeply cleft. 



The animals of this genus are much compressed, 

 slender in form, and colourless creatures. The eyes 

 are wanting or rudimentary. # The superior antennae 

 are very slender, longer than the inferior, and carry a 

 very small secondary appendage. The mandibles are 

 furnished with a tri-articulate appendage ; and the foot- 

 jaws have the squamiform plates but slightly developed. f 



* Caspary (Verhandl. d. Naturf. Vereins fur Rheinland, Jahrg. 6.) and 

 Hosius (who kept specimens of iV. puteanus alive for many weeks) were 

 unable to detect any traces of eyes ; but Grervais (Ann. Sci. Nat. 2 ser. iv. 

 p. 128) considered that the species possessed eyes although destitute of 

 coloured pigment. In all that we have kept alive, some for several weeks, as 

 in N. fontanus, they are imperfectly formed and of a lemon colour. 



+ The first and second maxiiloe and the foot-jaws do not materially differ 

 from those of Gammarus pulex. Hosius indeed figures the first maxilla in 

 N. puteanus as having a very slender ex-articulate palpus, but our dissections 

 agree with those of Schiodte, showing the palpus to be broad and two-jointed. 

 It is probable that the specimen of N. puteanus dissected by Hosius was im- 

 mature, as the palpus in very young specimens of G. fiuviatilis, as also figured 

 by Hosius, is also slender, and with the joints only indistinctly exhibited. 



