396 Mr. G. W. Kirkaldy on the 
synthlipsis, being of great convenience for diagnostic 
purposes. The imaginary anterior margin of the noto- 
cephalon is called the vertex. The junction of the meta- 
thorax and abdomen has been taken as the centre of the 
insect. This will explain why the tip of the scutellum 
is called its “ base,” and why the ‘third side” is termed 
its “ apical margin.” 
Heap. Antipalocoris and Signoretiella are at once 
recognised by the contiguity of the eyes basally; in 
Anisops the notocephalon is very narrow, in the other 
genera wider. In Anisops the labrum attains to the apex 
of the second rostral segment, in Notonecta, Enithares, 
and Martarega to about the centre of that segment; 
Berg and Scott do not mention it. The ultimate and 
penultimate antennal segments are subequal in Hnithares 
and Martarega; the ultimate is much the longer in 
Anisops and Antipalocoris,and much the shorter in Noto- 
necta and Signoretiella.* The scutellam in Notonecta is 
large and almost equal in length to the metanotum, 
except in N. mexicana, where it is only about half its 
length; in Enithares and Martarega it is about half, and 
in Anisops and Antipalocoris about one-third the length 
of the metanotum. Berg does not mention it in 
Signoretiella. 
The Hemretyrra are divided into clavus, corium, and 
membrane in Notonecta, Hnithares, and Anisops, and these 
genera are furnished with ale, which are wanting in the 
other genera, in which also the hemielytra are not or at 
least very obsoletely divided into areas. 
Pepes. The length of the pedes in Antipalocoris 
readily distinguishes that genus, the apices of the 
* T regret that I cannot altogether agree with Berg’s account of 
the antennal segments (An. 8. Cient. Argent., xvi., p. 122). He 
believes that the antenne in Notonecta and S/gnoretiella have five 
segments. Iamunable to speak with regard to the latter genus, 
but judging from preparations in glycerine jelly of four species of 
the former, examined under a compound microscope, the third 
segment of Berg appears to be only a muscular articulation 
between the true second and third segmente. The basal segment, 
which Berg thinks may be an antenniferous tubercle (tubérculo 
antenar), seems in structure, texture, and method of articulation, to 
be a true antennal segment. 
