L. Harrison 
389 
flange is reduced, and the cleft has disappeared. The Colpocej)halum 
condition can be reached from Eomenojpon by cutting away that part of 
the forehead between the frontal cleft and the eye. Species in exactly 
this condition occur upon the cockatoos. It seems to me that the 
Eomenopon condition may have given origin to two divergent hnes, 
one of which has become Menopon, the other Colpoeephalum ; and that 
possibly, as more forms are carefully examined, a more or less complete 
FiR. 1. Outlines of one side of the head of (1) Menopon sp., (2) Eomenopon, (3) Heterodoxns. 
The dotted line indicates the anterior ventral border of the antennary fossa. 
phyletic series may be obtained. The relation of the Menoponidae to 
the Boopidae still remains an open question. Cumming’s genus Tri- 
menopon (1913, p. 40) may partly prove to bridge the gap; and, as far 
as head-structure goes, Eomenopon shows a somewhat intermediate 
condition. But the Boopidae possess some structures not found in 
any other Mallophaga, and their precise relationship cannot be estab¬ 
lished in the present state of oiir knowledge. 
Genus Machaerilaemus, nov. 
Two genera 'of Menoponidae have already been estabhshed chiefly 
on account of peculiar chitinous structures in the gular region, viz. 
Ancistrona Westwood (1874, p. 197), and Pseudomenopon Mjoberg (1910, 
p. 50), found upon petrels and rails respectively. To these I now add 
a third, from an Australian gra.ssfinch, which bears a remarkable 
chitinous plate upon the throat. The genus may be characterised as 
follows: 
Menoponidae with very broad head, more than twice as wide as 
long, bearing on the throat a large squarish chitinous plate, flanked by 
