252 NEW YORK STATE MUSEUM 



veloped in the two following cases. is the conjoined penis and 

 seminal vesicle, developed on the anterior portion of segment 3. 



These conditions are typical of the Libellulidae. Genital 

 lobes, not indicated in this figure (but shown at gl in figure 17), are 

 characteristic of this family. These occur just outside the 

 hamules and in most cases are well chitinized and hairy. They 

 are lobelike continuations of the tergite of segment 2. The 

 penis found attached to the vesicle on segment 3 in this sub- 

 order extends much further on segment 2, but the sketch was 

 made to present as clearly as possible the relations of all the 

 structures and were the penis in its exact place, several other 

 structures would be hidden. 



In the next figure {c) we show conditions representative of 

 parts as found in family Aeschnidae, differing only in degree 

 from those found in the Libellulidae. Here the anterior lamina 

 (f) is cleft in the middle to accommodate the ovipositor pos- 

 sessed by the female in this family, which is directed forward 

 in copulation. At the hind angles of the anterior lamina there 

 is developed another pair of hamules, the anterior ones, clearly 

 marked and extending posteriorly to meet and cover the sup- 

 porting framework m. Where these first hamules are not 

 clearly developed, there is found in all cases a marked develop- 

 ment of the anterior lamina and in most cases a tendency 

 toward the formation of the anterior hamules. For example, 

 in Gomphaeschna one pair, the posterior, hamules are found. 

 But seemingly to compensate for what is attained by the de- 

 velopment of a second pair, the anterior lamina is highly dif- 

 ferentiated, the sheath of the penis is barbed and peculiar lobes 

 are developed on the seminal vesicle which seem to function 

 somewhat like the genital lobes of the Libellulidae. Where 

 genital lobes are well developed, two pair of hamules do not 

 appear. 



At .y is shown a well developed sheath entirely corresponding 

 in position with that of the former figure, only more specialized. 

 This sheath is supported by a framework only a little more com- 

 plicated than the framework among the Libellulidae, more chitinized 

 in every point and especially marked in the better development of 

 the posterior portion n which is only a line in figure {b) . It is 

 easily seen that the framework is homologous with that of the 



