This palm has the stem from eight to twelve feet high, irregularly ringed, and armed with long scattered black spines. The leaves are terminal and of moderate size, regularly pinnate, the leaflets spreading out uniformly in one plane, elongate, acute, with the terminal pair shorter and broader. The petioles and sheathing bases are thickly covered with long black spines generally directed downwards, and often eight inches long.

The spadices grow from among the leaves and are simply branched and spiny, erect when in flower, but drooping with the fruit. The spathes are elongate, splitting open and deciduous. The fruit is of a moderate size, oval, of a yellowish colour, and with a small quantity of rather juicy eatable pulp covering the stony seed.

On the Upper Amazon cattle eat the fruits of the Murumurú, wandering about for days in the forest to procure it. The hard stony seeds pass through their bodies undigested and become thickly scattered over the pastures adjoining the houses. They are so hard that it is almost impossible to break them, except by a very hard blow with a large hammer. The internal albumen or kernel is also excessively hard, nearly approaching to vegetable ivory. Yet pigs are very fond of these little cocoa-nuts, and on one estate on the Upper Amazon where I was staying, they had scarcely anything else to eat during a part of the year but those which had passed through the stomachs of the cows. They might constantly be seen cracking the shell with their powerful jaws, and grinding up the hard kernels, on which the teeth of few other animals could make any impression. They not only existed on this food, but in some cases got actually fat upon it. The black vultures (Cathartes) occasionally eat the outer covering of this and other palm fruits, when hard-pushed for food.

This tree grows on the tide-flooded lands of the Lower Amazon and on the margins of the rivers and gapós of the Upper Amazon, though it is possible that the two may be distinct species. The specimen figured is from near Pará. There are living plants in the Palm House at the Royal Kew Gardens.

A portion of a leaf is enlarged to show the spines, and a fruit is represented of the natural size.