ORDER AMPHIPODA — GAMMARUS, 37 
GENUS GAMMARUS. Fabricius. 
Antenne with the last joint composed of numerous minute ones; upper antenne as long or 
longer than the lower, with four articulations, the last ending in a bristle; lower antenne 
with five articulations. Feet fourteen; the two anterior pair monodactyle, subequal; the 
two following pair terminate in a simple curved nail. Tail with small fasciculate spines 
above, and bifid ones at the tip. 
GAMMARUS MINUS, 
PLATE IX. FIG. 29. 
Gammarus minus. Say, Jour. Acad. Nat. Sciences, Vol. 1, p. 376. 
Description. Body incurved, subcompressed. Upper antennz longest, with the sete short, 
attaining the tip of the second articulation of the terminal joint, which has about twelve arti- 
culations. Eyes reniform. 
Color. Body whitish, with a few pale fulvous spots on the sides. In dried specimens, the 
color becomes reddish, and the lateral spots, more particularly towards the tail, are bright 
red. 
Length, 0:15-0°3. 
This species is common in most of our fresh-water streams, and may often be detected 
under stones and pieces of wood. It is extremely active, and is popularly known under the 
name of Fresh-water Shrimp. 
(EXTRA-LIMITAL ) 
G, mucronatus. (Say, loc. cit. p. 376.) Antenne subequal. Eighth, ninth and tenth segments of the 
body mucronate above, more distinctly on the female. Length, 0+4. This and the succeeding 
will in all probability be found in this State. Inhabits the coast from New-Jersey to Florida. 
G. fasciatus. (Ip. Ib. p. 374.) Eyes at the outer base of the antenna, reniform; terminal joint of the 
upper antenne with about thirty articulations. Color, whitish, fasciate with faint green which 
becomes reddish after death. Length, 0°4. Fresh water. Pennsylvania. 
G. locusta. (Montacu, Lin. Tr. Vol. 9, p. 359, pl. 4, fig. 1. Gouxp, loc. cit.) Eyes linear, almost 
lunulated ; antenne covered with hairs; threads of the caudal appendices subequal. Allied to the 
preceding. Massachusetts. 
G. appendiculatus. (Say, 1. ¢. p. 377.) Caudal segments, and three terminal segments of the body, 
dentated on their posterior edges, Feet in one sex with the second pair didactyle. Length, 0°3. 
Georgia. 
