256 NEW YORK STATE MUSEUM 
here we have the least specialized external genital parts, how- 
ever, all structures here present are found in both suborders and 
in all are easily homologized with those in Perithemis. 
In figure 22 three variations, found in other families of Anisop- 
tera, in the structure of the supporting framework are shown, 
«+ from Ophiogomphus, y from Epiaeschna and zg from Gom- 
phoides. If one compares these with Perithemis, figure 20, it may 
be easily seen that all are 
constructed on the same 
general form. Ophiogom- 
phus (1) shows perhaps the 
most complex condition 
owing to the new lines of 
ae Chitinys at 05) leetierumma 
bE ige, 22 refers to that bar of chitin 
which is produced under the anterior lamina and passes posteriorly 
directly under the base of the sheath s in each case. The sheath 
here and in the following figures is much more chitinized and in 
every way better developed. In Epiaeschna (y) the posterior por- 
tion of the framework is extremely chitinized and enlarged over 
that of Perithemis. The hamules are very large with a correspond- 
ing enlargement of the framework to which they are attached. The 
two bars passing on each side of the sheath and below it correspond 
of course to e in (v7). As far as the support of the sheath is 
concerned, this seems to represent a transition between (1) with 
the lines at w fully developed and (2) with the indications of such 
lines entirely lacking. One can easily note in (y) the stumps of 
processes which are homologous, as far as they go, to lines u 
a (2). 
Perhaps the spatial relations of these complicated parts will 
be better shown by a diagram of the median plane. Figure 23 
presents a sagittal section of the inverted ventral part of the 
2d segment in both suborders, with homologies indicated as — 
far as possible. These are views from the interior, (m) being 
the inside view of Zygoptera and (7) that of Anisoptera. 
In (m) the anterior lamina is marked /. It passes poste- 
riorly just over the anterior portion of the framework which 1s 
just below the penis at e. The under side of the lamina is 
