Holotype worker. TL 80, HL 1.82, HW 1.78, CI 98, SL 1.16, SI 65, PW 1.50, AL 2.22.
Mandibles with 6 teeth; with strong rounded longitudinal rugular sculpture. Median portion of clypeus bounded by a carina on each side which runs to the anterior margin. Median clypeal carina present, running to the clypeal notch. On each side of the median carina the clypeus with 2 - 3 weaker carinae which may be broken or discontinuous. Eyes large, maximum diameter 0.40, about 0.22 x HW, situated approximately at the midlengths of the sides and breaking the outline of the sides in full-face view. Frontal carinae sharply developed, roughly parallel and about 0.76 apart (c. 0.43 x HW) at the level of the midlength of the eyes. Posteriorly the frontal carinae sharply divergent and running towards the occipital corners as a raised crest on each side. Lateral marginations of pronotum extended outwards as a semitranslucent lamella on each side, the maximum width of which is c. 0.14. On the left side of the holotype the lamella is continuous from the pronotal corner but on the right the corner forms a separate angle, separated from the lamella proper by an indentation. Pronotum (including the lamellae) much broader than long. Promesonotal suture absent on dorsum centrally, but its former track indicated by a feeble indentation running across the unbroken strong longitudinal sculpture. Lateral parts of promesonotal suture on the dorsal alitrunk, and its track down the sides of the alitrunk, represented by a conspicuous cleft filled with very dense off-white pubescence. Mesonotum not marginate but armed with a low broad tubercle on each side. Promesonotum convex both longitudinally and transversely. Metanotal groove impressed, narrow. Propodeum weakly and irregularly marginate laterally, armed with a pair of small denticles. Dorsum of propodeum rounding evenly into the short declivity; the dorsum between the denticles transversely shallowly concave. Metapleural lobes conspicuous, deep and broad. Peduncle of petiole thick, with a low and rounded anterior process ventrally. Petiole node in profile low and roughly triangular, tapering dorsally to a narrow peak which is inclined backwards from the vertical. In anterior view the dorsum of the petiole node emarginate and armed with a pair of low, broad triangular teeth. Postpetiole in profile rising to a sharp peak dorsally. In dorsal view this peak is seen to be the topmost point of a knife-edged transverse crest which falls away on each side, separating the anterior face of the postpetiole from the rest. Dorsum of head between the frontal carinae with eight roughly parallel, quite widely separated, strong longitudinal costae; the spaces between them with superficial granular ground-sculpture. Sides of head between frontal carinae and eye rugose, with granular ground-sculpture between the rugae and with a few cross-meshes above and in front of the eye. Sides of head below and behind eye strongly sulcate. Sides of pronotum strongly sulcate, the sulci inclined slightly backwards from the vertical. Remainder of sides of alitrunk longitudinally rugose except in the area below the propodeal margin where the rugae are irregular. Promesonotal dorsum strongly and regularly longitudinally sulcate. Propodeal dorsum with some longitudinal rugulae on the anterior half but behind this the surface merely superficially reticulate. Anterior faces of both petiole and postpetiole with fine superficial reticulation, the latter also with some low rugae which radiate from the petiolar junction. Posterior faces of both segments with coarse rugae. Basal third of first gastral tergite densely longitudinally costulate, the spaces between the costulae smooth or nearly so. Posteriorly, as the costulae fade out, a fine superficial reticulation or shagreen-ing fades in, and this continues to the hind margin of the sclerite. All dorsal surfaces of head and body with numerous short white hairs. Femora and tibiae with numerous standing hairs. Black, the mandibles, antennae and legs dark brown.
Holotype worker, Madagascar: Foret de Zombitsy, near Sakaraha, 650 m, 16. xii. 1959 (no collector's name) (MCZ, Cambridge).
The shape of the postpetiole allies xaltusHNS to rufipesHNS, but this latter is a much smaller species with simple pronotal margination and less regular pronotal sculpture. The following key will separate the known species of the Malagasy region.