NEW FORMICID^; FROM BARRO COLORADO ISLAND. 173 



short and robust, the pro- and mesonotum forming a mass which 

 is very convex and subangulate above in profile, the posterior 

 surface of the mesonotum descending perpendicularly to the 

 pronounced mesoepinotal constriction. From above the meso- 

 notum is semicircular in front, with rather prominent humeri, 

 behind which the sides are straight and converge to the meso- 

 epinotal constriction. Epinotum as long as broad, much lower 

 than the promesonotum, with subequal base and declivity and 

 two backwardly directed spines which are slightly longer than the 

 width of their bases and nearly as long as the base of the epinotum. 

 Petiole small, about i| times as long as broad, the peduncle 

 distinct and parallel-sided, the node strongly compressed antero- 

 posteriorly, with abrupt anterior and more sloping posterior 

 surface and entire, distinctly transverse superior border. Post- 

 petiole nearly half again as broad as the petiole; transversely 

 elliptical, convex and rounded above and on the sides. Gaster 

 smaller than the head, elongate-elliptical, with slightly concave 

 anterior border. Femora and tibiae distinctly thickened and 

 clavate. 



Shining; mandibles and clypeus smooth and very sparsely and 

 finely punctate. Remainder of head densely punctate and trans- 

 versely rugulose, the rugules most distinct on the front. Thorax 

 and petiole densely and finely punctate, somewhat more coarsely 

 on the promesonotum. Postpetiole and gaster very smooth and 

 shining, the latter with a small punctate area near the insertion 

 of the postpetiole. 



Hairs yellowish, rather long and coarse, erect or suberect, 

 moderately numerous, longest on the abdomen, sparser and some- 

 what shorter on the legs. 



Brownish black, mandibles, sides of clypeus, antennae and legs 

 piceous; tarsi brownish yellow. 



Worker. Length I mm. 



Head as broad as long, subrectangular, with distinct but 

 rounded posterior corners, nearly straight posterior border and 

 feebly convex sides. Mandibles with 7. small teeth, the second, 

 fourth and sixth from the apex very minute. Clypeal border 

 with four or five minute denticles which are the anterior termi- 

 nations of longitudinal rugules. Eyes moderately convex, as long 



