256 



NEW YORK STATE MUSEUM 



Z' 



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, 

 X from Ophiogomphus, y from Epiaeschna and 2 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 (jr) shows perhaps the 

 most complex condition 

 owing to the new lines of 

 chitin at u. Letter e 

 refers to that bar of chitin 

 which is produced under the anterior lamina and passes posteriorly 

 directly under the base of the sheath ^ 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 (x). As far as the support of the sheath is 

 concerned, this seems to represent a transition between (x) with 

 the lines at u fully developed and (z) 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 

 in (x). 



Perhaps the spatial relations of these complicated parts will 

 b^ 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 (n) that of Anisoptera. 



In (m) the anterior lamina is marked /. It passes poste- 

 riorly just over the anterior portion of the framework which is 

 just below the penis at e. The under side of the lamina is 



