246 
Arcfas persiciis 
by a deep cleft into two unequal parts:— (a) a smaller narrowly crescen¬ 
tic area which forms the anterior and the greater part of the lateral 
margin, and {b) a larger postero-internal area which fills in the 
remainder of the rounded contour of the spiracle (see Part I, PI. Ill, 
fig. 6). As previously stated, the anterior crescentic area is perforated 
by innumerable fine pores, while the larger postero-internal portion of 
the spiracle is formed of stout cuticle which differs but little in 
appearance from those parts of the general cuticular investment of the 
body from which the scutellae are absent (see Part I, p. 29). 
mac. 
Fig. 6. Argas persiciis <? . Transverse section through the spiracle and atrium. The 
section is orientated in its natural position, x 380 diam. 
Text-figure 6 represents a transverse section through the spiracle 
and immediately underlying parts. The lower portion of the figure 
shows the postero-internal imperforate area {mac.), which is separated 
from the perforated crescentic portion {a. por.) by the above-mentioned 
deep cleft (os.). In the upper portion of the left half of the figure, 
a hollow chamber of irregular form—the atriam (at .)—is seen to project 
