416 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
little broader, broadest behind, sides nearly straight; in profile 
gradually elevated from base to angle of declivity; declivity half as 
long as the basal part, with the surface flattened. Petiole from 
above very little broader than long, anterior margin straight, at 
corners of base with prominent lamellate projections, that appear as 
spines from above; sides rounded, posterior border feebly rounded; 
in profile deeper than thick, with nearly straight anterior and posterior 
surfaces, slightly convex above. Gaster.cylindrical, strongly nar- 
rowed toward apex; the first segment noticeably broader than the 
second and equal to it in length; a distinct ventral spine present at 
base. Sting comparatively large. Legs very slender. 
Head, thorax, and petiole subopaque, closely, foveolately punctate 
throughout; pleurae of pro- and mesothorax and anterior coxa 
obliquely rugulosely striolate; collar transversely rugulose-striolate. 
Mandibles shining, finely punctate. Antennae and legs subshining, 
finely punctate. Gaster shining, minutely punctate. 
Body, legs, antennae, and mandibles with semierect pilosity. 
Head, mandibles, thorax, and petiole fuscous to piceous; borders 
of the frontal lobes, a round spot on the pronotum, the gaster and 
legs red. The borders of the gastric segments are infuscated. 
Described from several specimens taken at Camp 39, Madeira- 
Mamoré R. R. The colony was discovered quite accidentally by 
scratching away some of the leaves and debris with which the ground 
in the forest is always covered. As far as I could ascertain the ants 
were traveling in a definite direction. Some of those before me are 
red in color, evidently immature. Nothing seems to be known re- 
garding the habits of the species of this interesting genus, specimens 
of which are rare in collections. The four known species have each 
been found only once. 
38. Ponera trigona Mayr. 
One small colony was found at Manaos. 
39. Ponera opaciceps Mayr. 
Several colonies were taken at Ceardé-Mirim. 
40. Ponera distinguenda Emery. 
Numerous workers were taken at Camp 39, Madeira-Mamoré R. R. 
