256 DIVISION III. ARTICULATED ANIMALS.—CLASS I. CRUSTACEA. 
used for bait for anchovies. The fishermen gather them in a short time be- 
fore they cast their shelf, and preserve them in baskets until the moulting 
process has been effected, when they are reckoned a delicacy even on the 
best tables. On attempting to seize this crab, it runs rapidly sidewise, and 
conceals itself in the mud ; but when unsuccessful, it raises itself with a men- 
acing mien, beats its claws noisily together, as if in defiance of the enemy, 
and prepares for a valiant defence, like a true knight. 
In 
those which have been called sea-spiders they are very long, thin, and weak, 
The legs of the crabs are very differently formed in various species. 
so that the animal swims badly, and is a slow and uncertain pedestrian. 
For greater security, it therefore generally seeks a greater depth, where, 
concealed among the sea-weeds, it wages war with annelides, planaries, and 
small mollusks. Sea-spiders are often found on the oyster banks, and con- 
sidered injurious by the fishermen, who unmercifully destroy them whenever 
they get hold of them. 
In other species the legs are short, muscular, and powerful, so as rapidly 
to carry along the comparatively light body. The tropical land-crabs and 
the genera ocypoda and grapsus, which form the link between the former 
and the real sea-crabs, are particularly distinguished in this respect. 
The rider or racer (Ocypoda cursor), which is found on the coasts of 
Syria and Barbary, and abounds at Cape de Verde, owes its name to its 
swiftness, which is such that even a man on horseback is said not to be able 
to overtake it. The West Indian ocypodas dig holes three or four feet deep, 
immediately above high-water mark, and leave them after dusk. Towards 
the end of October they retire farther inland, and bury themselves for the 
winter in similar holes, the openings of which they carefully conceal. 
A strange peculiarity of many crabs is the quantity of parasites they carry 
along with them on their backs. Many marine productions, both of a vegetable 
and animal nature, have their birth and grow to beauty on the shell of the 
sea-spider.  Corallines, sponges, zoophytes, alg, may thus be found, and 
balani occasionally cover the entire upper surface of the body of the crab. 
“All the examples of the Zvachus Dorsettensis which I have taken,” says 
the distinguished naturalist Mr. W. Thomson, of Belfast, “were invested 
with sponge, which generally covers over the body, arms, and legs; alge 
and zodphytes likewise spring from it.” In this extraneous matter some of 
the smaller zodphytes find shelter, and, together with the other objects, ren- 
der the capture of the Irachus Dorsettensis interesting far beyond its own 
acquisition. In Mr. Hyndman’s collection there is a sea-spider curying on 
its back an oyster larger than itself, and covered besides with numerous 
barnacles. 
Tuetrnusa.—The Thelphuse have the ocular peduncles longer than 
