88 
Psyche 
[September 
Oncopodura ambigua n. sp. 
Plate 6, figures 1-5 
Facies typical for genus. White, without trace of pig- 
ment or eyes. All antennal segments subovoid. Antennal 
segment four equipped with an apical conical projection 
and four blunt oval “sensory” setae. Remainder of setae 
of fourth segment slender smooth and acuminate. Third 
antennal segment with apical organ of two elliptical rods, 
with marked ladder-like striations, without clearly visible 
central axis. Remainder of antennae covered with a mix- 
ture of smooth setae (as in fourth antennal segment) and 
heavy conical finely striate setae. Postantennal organ of 
six lobes, the anterior pair lying at right angles to the 
long axis of the head, and the remainder radiating back- 
ward from this. 
Tibiotarsus without any clearly spatulate setae. Unguis 
untoothed, with a definite “triangular lamella” and an 
opposing smaller but similar seta. Both structures are 
attached near the base of the unguis. Empodial appendage 
simple, external edge straight and equipped with a short 
apical filament. 
Mucro slightly shorter than dens, equipped with an 
apical and three dorsal teeth. A single large scale is at- 
tached to the base of the mucro. Dens clearly subdivided 
into two portions. Inner dorsal margin of dens equipped 
with four apically curved heavy ciliate setae. A sixth seta 
is on the outer margin near the base of the dens. Remainder 
of dorsal surface with one large scale and five acuminate 
smooth setae. 
Discussion 
In the series examined there was little variation out- 
side of relative size. The large ciliate setae upon the inner 
margin may be five in number. Occasionally the basal- 
most of these setae is not curved at its apex. 
The p.a.o. is often sunken into the head and it is very 
difficult to puzzle out the exact arrangement of the lobes. 
The presence of a definite triangular ungual lamella com- 
bined with the presence of a six-lobed p.a.o. immediately 
serves to distinguish this species from all those given in 
