t man are benumbed, and he is struck down
helpless, by a discharge from the battery of the gymnotus. The organs
which produce this curious electrical effect are placed along the under
side of the tail. They may be compared to a series of columns inclosed
in a thin membrane packed closely together, which, consisting of a
series of fiat discs, may be imitated by placing a number of coins with
their discs parallel to each other, and with a bladder between each,
separated by a gelatinous substance. These columns are technically
called septa; and La Cepede calculates that two hundred and forty
transverse membranes are packed in each inch, thereby giving to an
electric eel eight feet in length an organ cavity of two hundred and
forty-six square feet--an enormous extent, as may be supposed, of
electricity producing surface. The whole apparatus is supplied with
nerves which run through the entire length of the body.

STING-RAYS.

A fresh-water species of sting-ray is an inhabitant of the creeks and
lagoons of stagnant water; and so infested are some of them with the
creatures, that it is almost certain destruction to venture into them.
The sting-ray is circular and flat, with a tail above a foot in length,
very thick at the base, and tapering towards the end. Near the middle,
on the upper part, it is armed with a long and sharp-pointed sting,
finely serrated on two sides, which the fish can raise or depress at
will. When disturbed, by a quick movement of the tail out darts its
sting towards the object, which it seldom fails to reach. The wound
thus inflicted is so severe that the whole nervous system is convulsed,
the person becoming rigid and benumbed in a few moments. Long after the
most violent effects of the wound have subsided, the part affected
retains a sluggish ulceration, which has often baffled the skill of the
best surgeons.

They frequent the shallow banks of muddy pools, where they may be
constantly seen watching for their prey, and, as if conscious of their
powers, scarcely deign to move off when approached. They have their
enemies in vultures and other birds of prey; and as they are considered
fit for food, war with spear and talon is constantly waged upon them.

SERROSALMUS PIRAYA.

In the Orinoco another dangerous creature exists, called by the natives
piraya, with a head shaped somewhat like a sabre. The lower jaw is
furnished with a formidable pair of fangs, not unlike those of the
rattlesnake