1911] 



Wheeler — Two Fungus-Groicing Ants from Arizona 



99 



terior comers of the head. Vertex without a pair of short ridges, but each of the 

 inner orbits with a distinct ridge which runs obliquely and mesially and stops half 

 way between the eye and the ridge from the frontal carina of the same side. Anten- 

 nal scapes somewhat thickened just beyond the middle, reaching a little less than 

 \ their length beyond the posterior corners of the head. Thorax in profile with 

 deep mesoepinotal constriction; pro- and mesonotum convex; epinotum with sub- 

 equal base and declivity, the former slightly convex, the latter sloping and concave 

 Inferior pronontal spines prominent, with blunt tips; superior spines reduced to 

 angular projections, between which there is a pair of small blunt median protuber- 

 ances. Mesonotum on each side with two angular projections which are as large 

 as the superior pronotal pair and of similar size and shape. Extreme posterior 

 portion of mesonotum with a small blunt projection just in front of the mesoepinotal 

 constriction. Base of epinotum with four longitudinal ridges, the inner pair of 

 which is the more prominent, diverges somewhat posteriorly and terminates in the 

 spines, which are acute, a little longer than broad at their bases and directed up- 



Fig. 2. Trachymyrmex desertorum sp. nov. Worker; 

 a, head; h, thorax and abdomen seen from above; 

 c, same seen in profile. 



ward, backward and slightly outward. Petiole with a very short, narrow peduncle; 

 its node seen from above as long as broad, rectangular, with four longitudinal ridges; 

 in profile the node is pointed above, with subequal anterior and posterior slopes, 

 the former concave, the latter straight. Postpetiole twice as broad as the petiole, 

 nearly as long as broad, broadest just behind the middle; its posterior border excised 

 in the middle, with a rounded lobe on each side; dorsal surface somewhat impressed 

 behind, so that in profile the upper surface is convex and rounded in front and 

 concave posteriorly. Gaster suboblong, broadest behind the middle, with straight 

 sides in front and without any trace of a median dorsal furrow. Legs moderately 

 long and stout. 



Mandibles longitudinally striated, at least their apical portions and the border 

 of the clypeus shining; remainder of body opaque, finely granular, except the legs 

 which are very faintly shining. The various ridges and projections on the head. 



