612 
ARTICULATA. 
THE SAND-HOPPBE MAGNIFIED. 
presenting notliing but the smootli, convex surface of their scaly armor to the enemy. This 
family also includes the Pill-Bug, Armadillo pillularis. 
ORDER 4. AMPHIPODA. 
This order consists of animals mostly of small size, none of them exceeding two inches in 
length. They usually lire free in the water or burrow in sand ; a 
few species are parasitic upon fishes. The Common Sand-Hopper, 
Talitrus locusta, which may be met with in thousands upon the 
sands of European shores, is a well-known example of this family. Al- 
though its length is not much more than half an inch, it can leap 
several inches into the air, and the facility with which it escapes 
pursuit by burrowing into the soft wet sand is truly wonderful. 
The Beach-Flea, T. quadrifidus, is found under stones and sea- 
weed on ouv coasts. The European species, Gammarus pulex, 
is found commonly in fresh water, and is scarcely inferior to its 
marine relative in agility. The G. minus, one-third of an inch long, and called Fresh-water- 
Shrimp^ is a common American species, found under stones and pieces of wood. 
ORDER 5. UEMODIPODA. 
This curious little order includes only two families. The Cyamidce, or Whale-Lice, infest the 
different species of cetaceous mammalia. They often live upon the whales 
in such vast numbers that their victims may be recognized at a distance by 
the w^hitish tint of their skin. The Whale-Louse, Cyamus ceti, is found on 
the whales along our coasts. 
In the second family, the CaprellidcB, all the proportions of the body are 
reversed ; instead of being broad and flat, as in the preceding, it is long, slen- 
der, and nearly cylindrical. The Caprella geometrica swims by alternate curv- 
atures of the body ; it is found among sea-weed and sponges, and walks like 
the caterpillars called Measuring- Worms. It is common on our coasts. 
ORDER 6. XYPHOSURA. 
This order consists only of a single genus, Limulus, the King- Crab, which, from the locality 
inhabited by the commonest species, is frequently termed 
the Molucca Crab. It is among the largest of crustaceous 
animals, sometimes measuring as much as two feet in 
length. The body is composed of two divisions — an an- 
terior, crescent-shaped piece, or carapace, and a posterior, 
somewhat hexagonal piece, formed by the coalescence of the 
abdominal segments. From the posterior extremity of this 
second division of the body, projects a long, spine-like tail, 
which exhibits no trace of segmentation. The upper sur- 
face of the body is convex ; the lower surface, on the con- 
trary, is concave in the middle, forming a hollow, in which 
the feet are lodged. These curious animals appear to be 
confined to the coasts of the East Indies and America. The 
species common on our own shores, Limulus Polyphemus of 
Milne Edwards, is called Horse-Foot. It is often used for 
feeding hogs, and the shell is employed as a ladle. The French 
colonists of the south called it Casserole-Fish from its re- 
semblance to a saucepan : the latter name is often given to 
it among us. The Indians used to point their arrows with 
THE KING-CRAB ou HOESE-FooT. the sharp homy tail. 
THE WHALE-LOOSE. 
