There are several kinds of piranha, many of which abound in the waters of the Tapajos. The piranha, called also the caribe, is a kind of salmon (Tetragonopterus). They are caught with any kind of bait, their taste being indiscriminate, and their appetite most ravenous. They frequently attack the legs of bathers near the shore, inflicting severe wounds with their strong triangular teeth. THE DIODON. The smaller inhabitants of the ocean are also represented in these fresh-waters. The little mamayacu, a species of diodon, which in the ocean attains a foot in length, is found in the Amazon three or four inches long, of a pretty green colour, banded with black. On being caught--which it easily is--it becomes in the hand as round as a ball. The natives, when a person gets corpulent, tell him that he has grown as fat as a mamayacu. The ocean species, from having the skin about the abdomen looser than that above, floats, when it becomes distended with air, with its back downwards. It can thus move about as rapidly as in its usual position, by aid of its pectoral fins. By the movement of its jaws it makes a curious noise, and can give with its sharp teeth a severe bite. The skin is also covered with small spikes, which, when thus inflated, become erect and pointed. It thus, though at first sight looking as helpless as can be, is well able to defend itself. The diodon has been known to be swallowed alive by a shark, in whose stomach it was found floating, probably supported by the air with which it had become inflated. It is asserted that it also frequently eats its way, not only through the coats of the shark's stomach, but through the sides of the monster, which is thus killed. Probably the little diodon of the Amazon has a similar means of revenging itself on the voracious monsters to whom it falls a prey; and though it might not be able to liberate itself through the scaly back of an alligator, it would inevitably kill the monster, or cause him such pain as to make him repent having swallowed so indigestible a morsel. The magnificent pirarucu or anatto, of vast size, with its ornamental coat of mail, and broad large scales margined with bright red, peoples the waters in immense numbers. It is most frequently caught by the native fishermen; and when salted, forms the staple food of all classes on the banks of the Lower Amazon. It swims at great speed, and attains the length of eight feet when full-grown, and five feet in girth. The Indian name of pirarucu is given to it from the native words _pira_, fish, and _urucu_, red; in allusion, says Mr Bates, to the red colour of the borders of its scales. Among the other fish most frequently caught are the surubim and piraepieua (species of Pimelodus); very handsome fishes, four feet in length, with flat spoon-shaped heads, and prettily spotted and striped skins--two long feelers hanging from each side of their jaws like trailing moustaches. THE ACARA.