ght; they are so numerous that the Indians fill many baskets of
them. J. Hancock supposes that the fish carry a small supply of water
with them in their gill-cavity, which they can easily retain by closing
their branchial apertures. The same naturalist adds that they make
regular nests, in which they cover up their eggs with care and defend
them--male and female uniting in this parental duty until the eggs are
hatched. _Synodontis_ is an African genus and common in the Nile, where
the various species are known by the name of "Shal." They frequently
occur among the representations of animals left by the ancient
Egyptians. The upper part of their head is protected by strong osseous
scutes, and both the dorsal and pectoral fins are armed with powerful
spines. Their mouth is small, surrounded by six barbels, which are more
or less fringed with a membrane or with branched tentacles.

[Illustration: FIG. 3.--_-Malopterurus electricus_.]

The curious fact of some species of _Synodontis_ having the lower parts
darker than the upper, some being whitish above and blackish beneath,
appears to be connected with their habit of swimming in a reversed
position, the Belly turned upwards. This habit, known to the ancient
Egyptians, who have frequently represented them in that attitude, has
been described by E. Geoffrey, who says they nearly constantly swim on
their back, moving quite freely forwards and sidewards; but if alarmed,
they revert to the normal position to escape more rapidly.

The electric cat- or sheath-fishes (_Malopterurus_) have been referred
to the same section. Externally they are at once recognized by the
absence of a rayed dorsal fin, of which only a rudiment remains as a
small interneural spine concealed below the skin. The entire fish is
covered with soft, villose skin, an osseous defensive armour having
become unnecessary in consequence of the development of a powerful
electric apparatus, the strength of which, however, is exceeded by that
of the electric eel and the large species of _Torpedo_.

The electric organ of _Malopterurus_ differs essentially from that of
other fishes provided with such batteries, being part of the tegumentary
system instead of being derived from the muscles. It consists of
rhomboidal cells of a fine gelatinous substance immediately under the
skin. It is put into action by a single ganglionic cell at the anterior
extremity of the spinal cord. Contrary to what takes place in other
elect