ARTICULATA. lll 
Orper 5. Xienosura. This order is here restricted to the single genus 
Limulus (pl. 78, Jig. 34), which Burmeister makes a tribe, under the name 
of Pecilopoda, a name which has a very different value assigned to it by 
other authors. On this account we prefer the name given by Gronovius. 
The terms Epizoa and Parisita are also used in such a manner as to cause | 
confusion, being applied both to the Lernwzde and to the Anoplura or lice. 
Limulus is remarkable for the long, hard, and sharp caudal spine, with 
which spears are pointed in some countries. They are called king-crab on 
the coast of the United States, where they are collected as food for hogs, 
although these animals will not attack them until accustomed to such an 
unusual kind of food. The body is covered by a large anterior carapace, 
and a smaller posterior one, the gill feet are attached to the abdomen, and 
six pairs of strong articulated ambulatory feet to the thorax. The latter are 
present in the fossil species which have been discovered. The caudal stylet 
is wanting in the embryonic young, which differs from the adult in some 
other particulars. The species live upon animal food. 
Malacostraca. 
Orver 6. Isopopa. In this order the body is depressed and oval, and 
there are seven pairs of feet attached to the seven movable segments of 
nearly equal size which form the thorax ( pl. 78, jigs. 20-22). The young 
resemble the adult, but they have only six pairs of walking feet. Some 
of the species are parasitic upon fishes or Crustacea, and these have the 
organs of motion and the eyes rudimentary. Most of the species are marine, 
although some inhabit the fresh waters, and others the land, the last requiring 
damp localities to preserve their gills from desiccation. The four antenne 
are of a medium size, and directed in front, the first pair being in some 
cases rudimentary. The organs of manducation are well developed, the 
thorax occupies a great part of the body, the feet are armed with a single 
nail, and in some cases they are prehensile. The females have a corneous 
horizontal plate at the base of the feet, which forms a receptacle in which 
the eggs are hatched. The abdomen is in the form of a terminal plate 
above, and beneath it supports six pairs of organs, five of which are 
respiratory false feet, and the sixth takes various forms, according to the 
family. 
Milne Edwards divides the order into three sections, according to their 
walking, swimming, and sedentary habits. The first includes the Jdotecda, 
Asellide, and Oniscide ; the second the Sphwromide and Cymothoide, 
under a different mode of division from that of Latreille ; and the third the 
Epicarides or Bopyride, under two families. 
The walking /sopoda have the terminal false feet in the shape of 
operculums, or of projecting candal stylets, which are never flattened into 
swimming organs; the first pair of antenne are generally short or rudimentary. 
In the swimming /sopoda there is a large caudal fin provided with lateral 
expansions formed by the modified fourth pair of false feet. All the antennz 
have the same form, and the second pair are well developed. 
The sedentary Zsopoda are parasitic, and whilst the males present the 
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