252 NEW YORK STATE MUSEUM 
veloped in the two following cases. o 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 g/ 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 
(t) 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 s 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 which is only a line in figure (0). It is 
easily seen that the framework is homologous with that of the 
