92 CRUSTACEA. 



unique in this order — the internal' extremity of the third joint of the 

 peduncle is provided with a little articulated thread. It distin- 

 guishes the 



Gammarus, Lat., 



Where the four anterior feet have the form of small forceps, the 

 movable toe folding beneath. 



The species best known and the type of this subgenus is the 



Cancer pxilex, L.; Squillu pulex, De Geer, Insect., VII, xxxiii, 



1,2. It inhabits brooks, etc. The other species are marine(l). 



The antennae of the following, as in all the other Amphipoda, are 



simple or without appendages. 



Melita, Leach. 



The second pair of feet, in the male, terminated by a large com- 

 pressed forceps, the toe folding under its internal surface; the an- 

 tennae nearly equal in length; a small foliaceous appendage on each 

 side of the posterior extremity of the body(2). 



* 



M^RA, Leach. 



The second feet in the males terminated as in the Melitae, but the 

 toe folds under the inferior edge of the forreps and is not concealed. 

 The superior antennae are longer than the inferior, and the foliace- 

 ous appendages of the posterior extremity of the body are want- 

 ing(3). 



Amphithoe, Leach. 



The four anterior feet nearly similar in both sexes; the penultimate 

 article or hand proper, ovoid(4). 



Pherusa, Leach. 



The Pherusae only differ from the preceding subgenus in the hand 

 of the forceps, which is filiform(5). 



There, the peduncle of the antennae is only composed of two joints, 



(1) See Desmar., Consid., p. 265, 267. 



(2) Cancer palmatus, Montag., Trans., Lin. Soc, VII, p. 69; Encyclop. Method., 

 Atl. d'Hist. Nat., CCCXXXVI, 31: Desmar., Consid., XLV, 7- 



(3) Cancer gammarus grosimanue, Montag., Trans. Lin. Soc, IX, iv, 5; Desmar. 

 Consid. p. 264. 



(4) Cancer rubricatus, Montag., Trans. Lin. Soc, IX, p. 99; Encyclop. Method., 

 Atl. d'Hist. Nat., CCCXXXVI, 33; Desmar., Consid., XLV, 9;— Om'sews cancellus. 

 Pall., Spic. Zool. Fascic, IX, iii, 18; Gammarus cancellus. Fab. 



(5) Pherusa fusicola. Leach; Trans. Lin. Soc, XI, p. 360; Desmar., Consid., 

 p. 268. 



