This species grows in the Catinga forests of the Upper Rio Negro and on the margins of small streams, climbing over trees and hanging in festoons between them, throwing out its armed leaves on every side to catch the unwary traveller. How often will they seize the insect-net of the ardent Entomologist just as he is making a dash at some rare butterfly, or fasten in his jacket or shirt-sleeve, or pull the cap from his head! Woe then to the impatient wanderer! a pull or a tug will inevitably cause a portion of the fractured garment to stay behind, for the “jacitára” never looses its hold, and it is only by deliberately extracting its fangs that the intruder can expect to depart unhurt. In some places small igaripés or forest streams are almost filled up with various climbing grasses and creepers, among which the “jacitára” holds a prominent place, and it is up these streams that the Indians often delight to fix their abode. In such cases they never cut down a branch, but pass and repass daily in their little canoes which wind like snakes among the tangled mass of thorny vegetation. They are thus almost safe against the incursions of the white traders, who often attack them in their most distant retreats, carry fire and sword into their peaceful houses and take captive their wives and children. But few white men can penetrate for miles along a little winding stream such as is here described, where not a broken twig or cut branch is found to show that a human being has ever passed before. Thus does the thorny “jacitára” help to secure the independence of the wild Indian in the depths of the forests which he loves. This species most nearly agrees with the _D. macroacanthus_ of Martius. Fine specimens of an allied species may be seen growing in the Palm House at Kew. A fruit is represented on the Plate of the natural size. Genus BACTRIS, _Jacquin_. Male and female flowers intermingled in the same spadix, the females being more abundant in the lower parts and the males in the upper. Spathe double, exterior short and membranous, interior complete, woody. Male flowers with six, nine or twelve stamens. Female flowers with three sessile stigmas, and the stamens represented by a rudimentary ring. The stems in this genus are very slender, ringed, nearly smooth or with a few scattered spines. The leaves are more or less terminal, generally few in number, pinnate or entire, with the bases of the petioles much sheathing and very spiny. The spathe is also clothed with spines. The spadices are simple or simply branched and grow from the axils of the leaves. The fruit is small and round, and the outer pulp is often subacid and eatable. This very extensive genus of small prickly Palms contains forty-six species, all natives of South America. Two species described by Martius are here figured, together with six others apparently new, but as it may be impossible to identify those not seen in fruit, some of them have been left unnamed.