326 
GAMMA RIM. 
A MPH1P0DA . GA MM A RIDES. 
NATAT0B1A. 
Genus— CRANGONYX. 
Crangonyx. Spence Bate, Proceed. Dubl. Univ. Zool. and Bot. Assoc. 
1859. Nat. Hist. Rev. vol. vi. p. 165. Cat. Amph. Crust. 
Brit. Mus. p. 178. 
Generic character. Superior antennae having a secondary 
appendage. First pair of gnathopoda rather larger than the 
second. Posterior pair of pleopoda unibranched, not longer 
than the preceding pair. Telson single, entire. 
In this genus the eyes are imperfectly developed. 
The superior antennae are not much longer than the 
inferior, but rather more robust, and furnished with a 
secondary appendage. The first two pairs of legs are 
small, rather unequal in size, and subchelate. The 
caudal appendages are short, and the last pair terminate 
in a single branch, not longer than the preceding pairs. 
The terminal central plate is also single. 
This genus, like the last, belongs to the subterranean 
Fauna. A single species as yet is all that has been 
found in England ; but we have little doubt but that 
Gammarus Ermanni of Milne Edwards, which was found 
by M. Ermann in the warm springs of Kamschatka, 
belongs also to this genus. 
It is curious that we should have to record, that while 
the animals of this genus (as in the preceding) inhabit 
the deep artificial wells, without being known to exist 
in our rivers and streams, its nearest allied form is to be 
found in a marine genus, Gammarella. 
