406 © BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Workers are often seen moving slowly about or remaining motion- 
less on the stems and leaves of trees and shrubs. The species is 
partly nocturnal in habit and often enters houses and hunts about for 
other insects that come to the lights. A nest which I dug out was in 
the ground among the roots of a plant, about twelve inches below the 
surface. 
13. Ectatomma (Ectatomma) confine Mayr. 
Plate 1, fig. 8. 
A single worker (Plate 1, fig. 8), which agrees well with Mayr’s 
description, was taken at Porto Velho. Apparently the species has 
not been recorded since Mayr described it from a Colombian specimen. 
The structure of the pronotumr is very characteristic. The middle 
tubercle is prolonged and flattened above, and laterally compressed 
in front of the pleural spines so that it has the form of a short, thick 
carina. The lateral spines on the pronotum are short, flattened, and 
triangular; the epinotal spines are prominent. The sculpture of the 
head is coarse, that of the rest of the body delicate. The head, 
thorax, and abdomen are sparsely beset with coarse, erect hairs. 
14. Ectatomma (Gnamptogenys) concinnum (F. Smith). 
Plate ijedig. 7: 
Workers (Plate 1, fig. 7) were found at Porto Velho, Abunda, and 
Madeira-Mamoré Camp 39. 
15. Ectatomma (Gnamptogenys) tortuolosum F. Smith. 
Plate 1, fig. 6. 
Worker. (Plate 1, fig. 6.) Length 7 mm. 
_ Head, excluding mandibles, a little longer than broad, with slightly 
convex sides, narrowly rounded posterior corners and concave border. 
Clypeus nearly as long as broad, the surface depressed; anterior 
border straight. Mandibles slender, the blade edentate. Antennae 
robust; scape thickened apically, extending one fourth its length 
beyond the occipital corners; funicular joints 1 to 3 elongate, sub- 
equal; joints 3-6 globose, a little longer than broad. Eyes moder- 
ately large, convex, situated at middle of sides of head. Thorax 
