ROOM IX.] NATURAL HISTORY. 27 
posterior leg terminated by very flat joints, of an oval or 
orbicular form, and calculated to act as fins in swimming. 
The last pair of legs in all the Swimming Crabs, is con¬ 
stantly furnished with these flattened joints, and in some 
species the preceding pairs have them also, but never so 
broad as those of the hind legs. The eyes of the Telescope 
Crab ( Podophthalmus spinosus ), are supported on very 
long slender pedicles, reaching from the middle of the an¬ 
terior margin of the shell to the lateral angles, and lodged, 
when at rest, in a groove on the edge. This is the only 
known recent species belonging to this genus. Here are 
also specimens of the Freshwater Crabs ( Thelphusoe ), which 
live in the rivers and streams of Italy, and the south of 
Europe, and are likewise found in Asia and America ; 
they are capable of existing a considerable time out of the 
water. One species, peculiar to the south of Europe and 
the Levant, ( Le Cartere de riviere of Rondeletius,) enjoyed 
great celebrity amongst the Greeks, for its supposed me¬ 
dicinal virtues, and is frequently represented on the coins 
of Agrigentum with the utmost accuracy. In this Case 
are likewise some Crabs peculiar to hot countries, which 
are remarkable for the rapidity of their motions, and other 
peculiarities. They live in holes, usually near the sea¬ 
shore or in the neighbourhood of water ; these holes are of 
a cylindrical form, oblique, and very deep, and several of 
them are generally found near together, but each hole con¬ 
tains only one inhabitant. When the animal of one of the 
genera belonging to this family ( Gelasimus ) is in its hole, 
it closes the entrance with its claw, one of which, some¬ 
times the right, sometimes the left, is commonly much 
larger than the other. These Crustacea have also a 
singular habit of holding up the large claw in front of the 
body, as if they were beckoning to some one at a distance, 
whence they have acquired the name of Calling Crabs 
(Cancer vocans, Linn.). What has been said of the rapid¬ 
ity of the motions of these Crustacea, is particularly ap¬ 
plicable to those of the genus Ocypode, which hide in holes 
in the sand on the sea-shore during the day, and leave 
them at sun-set. This case also contains specimens of the 
genus Pinnotheres, a very small race of Crustacea, which 
inhabit bivalve shells, and were supposed by some of the 
ancients to be consentaneous inmates with the animal, and 
c 2 
