ORDER AMPHIPODA. 209 



Atylus, Leach, {Atyhis carinatus, Leach.) 



All those which succeed, have the upper antennae as long, or 

 longer than the lower, and the head does not advance in the 

 manner of a muzzle. 



Here, as in the five following genera of Dr. Leach, the 

 peduncle of the antennae is formed of three articulations. 



Some present, in their superior antennae, a character unique 

 in this order; the interior extremity of the third articulation 

 of their peduncle has a small articulated thread. It dis- 

 tinguishes 



Gammarus, (proper) Latr. 



The four anterior feet are in the form of little claws, with the 

 talon, or mobile finger, folded underneath. {Cancer pulex, 

 Linn.) 



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

 amphipods, simple, or without appendages. 



Melita, Leach, 



Have the second feet terminated in the males, by a large 

 compressed pincer, with the talon folded under its internal 

 face ; the antennae are almost of equal length ; the posterior 

 extremity of the body presents, on each side, a small foliaceous 

 plate. {Cancer palmatus, Montagu.) 



M^RA, Leach, 



Whose second feet are likewise terminated in the males, by a 

 large compressed pincer, but the talon is folded back on its 

 inferior edge, and is not concealed ; the upper antenna are 

 longer than the lower, and the posterior extremity of the body 

 presents no foliaceous lamina. {Cancer gammarus grossi- 

 manus, Montagu.) 



Ampithoe, Leach, 



In which the four anterior feet are nearly identical in both 

 VOL, XIII. P 



