. The Australian zoologist. Zoology; Zoology; Zoology. 140 A RECLASSIFICATION OF THE ORDER ODONATA. Thus one of the main characters which at present separate the Order Protodonata from the Order Odonata is no longer of value. ^xi Ax2 Axj. Fig. 8. A second evolutionary line is exhibited in almost as complete a fashion, in the formation of the discoidal cell. It begins in the strong sigmoitfal waving of CuP and 1A in the Meganeuridae (Fig. 4) and is continued into the Ditaxineuridae and Kennedyidae with only a single important dif- ference, viz., that the number of cross-veins is very greatly di
. The Australian zoologist. Zoology; Zoology; Zoology. 140 A RECLASSIFICATION OF THE ORDER ODONATA. Thus one of the main characters which at present separate the Order Protodonata from the Order Odonata is no longer of value. ^xi Ax2 Axj. Fig. 8. A second evolutionary line is exhibited in almost as complete a fashion, in the formation of the discoidal cell. It begins in the strong sigmoitfal waving of CuP and 1A in the Meganeuridae (Fig. 4) and is continued into the Ditaxineuridae and Kennedyidae with only a single important dif- ference, viz., that the number of cross-veins is very greatly diminished. In none of these forms is a true discoidal cell developed, but it is possible in both Ditaxineuridae and Kennedyidae to indicate that particular cross- vein (the discoidal cross-vein, dv) which, later on, is destined to form the distal side of the quadrangle (discoidal cell). The "open discoidal cell" of such types as Permagrion, Permolestes, Hemiphlebia (forewing only and Chorismagrion (forewing only), is formed merely by a change in the character of this cross-vein dp, which begins as a short cross-vein, more or less at right-angles to the main veins which it connects, and develops into an oblique vein continuing the course of the arculus downwards. It will be abundantly clear, therefore, that if we desire to retain the Meganeuridae within the Protodonata on the ground that these forms possessed no true nodus, then it would be very difficult to omit some of the Lower Permian forms placed in the Protozygoptera and Protanisop- tera especially Kennedya. If, on the other hand, we desire to retain the Meganeuridae within the Protodonata because of the absence of a dis- coidal cell, then it is clear that Ditaxineura, Kennedya and allies would have to be removed to the Protodonata with them. Martynov is quite correct of course, when he states (1932, p. 17) that the affinities of the family Meganeuridae are much closer to the Prot- anisoptera and Anisoptera than t
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