APHIPOUA. 
217 
ORDER III. 
AMPHIPODA. 
The Amphipoda are tlie only Malacrostiaca witli sessile and im- 
moveable eyes, whose mandibles, like those of the preceding Crusta- 
cea, are furnished with a palpus, and the only ones whose subcaudal 
appendages, always very apparent, by their narrow and elongated 
form, their articulations, bifurcations, and other incisures, as Avell as 
by the hairs or cilia with which they are provided, resemble false or 
natatory feet. In the Malacostraca of the following orders, these ap- 
pendages have the form of lamiuBe. or scales ; here these hairs and 
cilia appear to constitute the branchite. Many of them, like the Sto- 
mapoda and the La3modipoda, have vesicidar bursae either between 
their feet or at their external base, the use of Avhich is unknown. 
Tlie first pair of feet, or that which corresponds to the second foot- 
jaws, is always annexed to a particular segment, the first after tlic 
head. The antennoe, wliich with a single exception — the Phroniinae, 
— are four in number, project, gradually taper into a point, and consist, 
as in the preceding Crustacea, of a peduncle and a single stem, or 
one furnished at most with a little lateral branch, and usually com- 
posed of several joints. The body is generally compressed and curved 
beneath posteriorly. The terminal appendages of the tail are most 
frequently styliform and articulated. Most of them sAvim and leap Avith 
facility, and ahvays laterally. Some inhabit springs and rivulets, and 
are often found in couples consisting of the tAvo sexes ; most of them 
hoAvever live in salt Avater. Their colour is uniform, A^erging on 
reddish or greenish. 
They may all be comprised in a single genus, that of 
• Ga.aimarus, Fab. 
Which Ave may subdivide, in the first place, into three sections, 
from the form and number of the feet. 
1. Those Avhich have fourteen feet all terminated by a hook, or 
in a point. 
2. Those Avhicli also have fourteen feet, but Achich are — the four 
last at least — simple natatory. 
3. Those AAdrich have only ten apparent feet. 
The first section is divided into tAvo. 
Some of them, — the Uroftkra, Latr., usually Iuia'c a large head; 
theantennre are freqAiently short, and in some but two in number; tlie 
body is soft. All the feet, the fifth pair at most exce})ted, are simple, 
the anterior are short or small, and the tail is cither furnished at the 
extremity AA’ith lateral fins, or is terminated bs-^ iioiuts or aiqjcndages, 
widened and bidentated, or forked at their posterior extremity. I’hev 
