. Annual report. New York State Museum; Science; Science. 26o NEW YORK STATE MUSEUM the supporting framework heretofore described. This is the sheath of one of the LibelhiUdae, Nannothemis. q and r show the same type of sheath a little more chitinized and much more reflexed up and over the penis, s is from Didymops and shows a transitional condition between those preceding and those following. Here the sheath is flat but chiti- nized entirely and reflexed more over the penis, t and u show the highest specialization of sheaths of ^^^- 2^ this type — thick, chitinized, in- terior surface flatten
. Annual report. New York State Museum; Science; Science. 26o NEW YORK STATE MUSEUM the supporting framework heretofore described. This is the sheath of one of the LibelhiUdae, Nannothemis. q and r show the same type of sheath a little more chitinized and much more reflexed up and over the penis, s is from Didymops and shows a transitional condition between those preceding and those following. Here the sheath is flat but chiti- nized entirely and reflexed more over the penis, t and u show the highest specialization of sheaths of ^^^- 2^ this type — thick, chitinized, in- terior surface flattened, and much reflexed for the reception of the penis. These were found among Aeschnidae. These sheaths of Cordulegaster and Tachopteryx are stiff, hard, black structures. They are supported by the framework the same as that indi- cated at X for Nannothemis. Figure 2y shows a more highly specialized type than in figure 26. This form of sheath seems to be better fitted to fulfil its function than the former type and in fact each sheath here is a very concave, hollow receptacle for the penis. p is the sheath of Gomphus, a very well chitinized structure with a fairly deep cavity for the reception of the penis, indi- cated by a cross-section of its deepest portion. x indicates the position of the underlying framework, q is the sheath of Gomphaeschna, one of a slightly different form in that the cross-section of its deepest part presents a wedge-shaped cavity. The other letters r, s and t represent other forms constructed on the same general plan as that of Gomphaeschna. In figure 28 the relative development of the hamules in the Anisoptera is shown, special attention being called to the de- velopment of the first or anterior hamule from the lamina. This is a series beginning with Cordulia shurtleffi and ending with Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of
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