168 Mallopliaga from South African Birds 
In the type of Machaerilaemus the mesothorax is separated from the 
metathorax, whereas in the new species described here these parts are fused 
together. 
The following table will serve to differentiate the three genera: Eomenopon , 
Machaerilaemus and Neomenopon: 
(1) Head not twice as wide as long, with a deep narrow cleft in the side of the 
forehead, extending to the inner border of the antennary fossa; chitinous 
framework for support of the mandibles present, extending backwards from 
the anterior margin of the head to form a pair of short free projecting spinous 
processes; meso- and metathorax distinct. Eomenopon. 
Head more than twice as broad as long, without a cleft in the sides of the 
forehead; no spinous processes attached to the chitinous framework when 
present. 
(2) Head with a large chitinous plate on the throat, flanked by two dagger¬ 
like processes (present or absent in M. laticorpus ?) with or without a central 
circular perforation; chitinous framework absent or present; meso- and meta¬ 
thorax distinct or fused. Machaerilaemus. 
No chitinous plate on throat; chitinous framework present; mesothorax 
fused with the metathorax. Neomenopon. 
Genus Machaerilaemus Harrison. 
Harrison (1915). Parasitology , vii. 389. 
Machaerilaemus plocei , n. sp. (Plate XII, figs. 1-3). 
Female. Ground colour pale brown, with darker markings of the same 
colour. 
Head slightly more than twice as broad as long across temples. Forehead 
flatly rounded in front, abruptly rounded and swollen at the sides, with six 
hairs on each side. Eye with two minute hairs. Temples rounded, with four 
long hairs and several shorter ones. Occiput slightly concave, with two 
median hairs just inside the margin, and two more on each side, of which the 
outer one is the shorter. The only other hairs present on the dorsal surface 
are: two hairs on the forehead situated midway between the lateral angles 
and the middle line, the outer one being slightly longer than the inner one, and 
a short hair a little distance above these. 
On the ventral surface the most conspicuous features are the chitinous 
framework, which has already been described; the gular plate and a more 
or less triangular plate on either side of this. The gular plate is heart-shaped, 
with a free projecting spinous process and five or six hairs on each side. 
Antennae with the two terminal segments indistinct. Palpi with the apical 
