826 On the Classification of the Linnean Orders [August, 
Owing to the specialized nature of the labial palpi, the mouth- 
parts of the Odonata are sufficiently sad generis and distinctive to 
prevent their being placed among the Orthoptera, even if the 
thorax were not so dissimilar. In the aborted labium and other 
mouth-parts of the Ephemerina we also have strongly-marked 
characteristics forbidding their being placed in the Orthoptera; 
were it not for the strong resemblance of the Termitide to the 
Orthoptera (Blattaria) probably no one would have thought of 
carrying the Pseudoneuroptera over into the Orthoptera. 
The relative proportion of the head and sclerites varies greatly; 
no general rule can be laid down as to the relative proportions of 
the epicranium and of the clypeus, or of the gular region. : 
On this account I had at one time decided to split the group 
into two, and to restrict Erichson’s Pseudoneuroptera to the Pla- 
typtera, and to adopt Latreille’s term Subulicornia for the Odo- 
nata and Ephemerina (Subulicornes of Latreille). It may, how- 
ever be best for the sake of clearness to retain Erichson’s order 
Pseudoneuroptera as he indicated it, and to dismember it into 
what may be regarded, provisionally at least, as three suborders : 
1. Platyptera (Termitide, Embidz, Psocidæ and Perlide = Corrodentia and O7- 
~~ thoptera amphibiotica in part). : 
2, Odonata (Libellulide), 
3. Ephemerina (Ephemeride). 
It is comparatively easy to give well-grounded differential char- 
acters for these three suborders. They are so distinct that they 
may. perhaps hereafter be regarded as entitled to the rank ot n 
orders, or the Pseudoneuroptera may be dismembered into the 
Pseudoneuroptera and Subulicornia (Odonata'and Ephemerina). i 
1. Platyptera—The body is flattened; the head horizontal. 
The pronotum is large, broad and square. The meso- and wa 
notum are remarkable on account of the imperfect differentiation - 
of the scutum and scutellum ; the latter is indefinite in outlines $ 
but very large. The flanks (pleurites) are, when long, oblique, OF q 
are short. The sternites are usually very large and broad.. There — 
are often eleven uromeres. Eo 
2. Odénata.—While the Odonata and Ephemerina are aee 
what alike as regards the form and venation of the fore wings, 
their mouth-parts and thorax they are entirely unlike. ao 
1 This name zat, flat, ttepdy, wing, in allusion to the wings which Pe e 
majority (the Psocidz folding their wings rather rgof-like) fold their wings ™ 
the back. The Isoptera of Brullé comprise the Termitida. a 
