On the following morning, before breakfast, I took a walk to a high ridge of gneiss rocks, which is at a little distance from the river, and found a variety of different kinds of _Cacti_. One of these was a great _Melocactus_ much larger than the one which is so common near Pernambuco; it grows in fissures of the rock where scarcely any soil exists, and its tough roots penetrate to such a depth, that they can with difficulty be withdrawn; living specimens of this (_Melocactus Hookerianus_, Gardn.) which I sent home, now exist in the collections at Kew and Glasgow. While lying in the canoe, waiting for the breeze, I heard a splashing noise in the water as of heavy rain, but on looking over the side, I found it to be produced by hundreds of small fish; so abundant were they, that having no hook, I had recourse to a bent pin fixed to the end of a thread, and thus in a few minutes I caught above thirty of them. I found them to belong to the tribe _Salmonidæ_, of which they form a very diminutive species, measuring from two to three inches in length, and from an inch to an inch and a half in depth; they are called by the Indians Piába; the two lower thirds of their depth is of a silvery-white, while the upper third is of a pale lead colour, being in general appearance not unlike a herring in miniature; they are extremely voracious and abundant, especially in shallow water, where they are caught in numbers by children; they make an excellent dish when stewed. From a young man who was fishing in a shallow part of the river with a hand-net, I obtained a few other kinds of fish, and among them one which is very much dreaded by the inhabitants of the banks of nearly all the lakes and rivers in the northern provinces; it is called Piranha by the Brazilians, and is also one of the _Salmonidæ_, belonging to the genus _Serasalmo_. It is commonly about a foot in length, but sometimes is as much as two feet long, being very much compressed laterally, and very deep; the back is of a dark brownish colour, and the belly yellowish white, both being thinly marked with reddish spots; the lower jaw projects a little beyond the upper, and both are armed with about fourteen flattish triangular-shaped teeth, upwards of a quarter of an inch in length, and very short. It is most voracious, and is consequently caught with difficulty. Many people are often severely injured by them whilst bathing, and I have repeatedly been shown the scars left by their bites. It is said that ducks frequently lose their legs, in consequence of their voracity, and it is even asserted that where they abound, cattle have been known to perish from their attacks, when going into the water to cool themselves, or to drink.