EURYSTHEUS, 
353 
AMPHIPODA. GA MM A R IDES, 
NATATORIA . 
Genus— EURYSTHEUS. 
Ewrystheus. Spence Bate, Rep. Brit. Assoc. 1855, p. 58. 
Ann. Nat. Hist. 2 ser. xix. p. 143. Cat. 
Amph. Crust. Brit. Mus. p. 196. White, 
Pop. Hist. Brit. Crust, p. 181. 
Gammarus (Division -| — |- s), Liljeborg, Ofvers. af Kongl. Yet. Akad. 
Forhandl. 1854, p. 455. 
Generic character. Pereion and pleon of equal length. 
Antennae subequal, long, and slender ; superior pair having 
a secondary appendage. Gnathopoda subchelate; second pair 
larger than the first. Posterior pair of pleopoda biramous ; 
rami equal. Telson cylindrical. 
The animals belonging to this genus have the body 
very long, being quite half the length of the entire 
animal. The antennae are long, slender, and sub-equal. 
The superior are furnished with a secondary appendage. 
The inferior originate posteriorly to the superior. The 
mandibles are furnished with an appendage. The first 
two pairs of legs are subchelate ; the second pair are larger 
than the first, although not of great size. The walking 
legs are long and slender, increasing in length posteriorly. 
The caudal appendages are biramous ; those of the 
posterior pair are not foliaceous. The terminal caudal 
appendage is developed in the form of a small segment, 
and probably the prim® vice debouches at its extremity. 
This genus may be distinguished from Mcera by the 
form of the head and the character of the middle tail- 
piece. 
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