^II-2 Zittle. Traite de Paleontologie t. II.
    Bull. U.S. Geol. Survey No. 31.
    Bull. U.S. Geol. Survey No. 69.
    Fossil Insects of North America. Vol. I. Pretertiary Insects.
    Index to the known Fossil Insects of the World, including Myriapods and Arachnids. Bull. U.S. Geol. Survey No. 7I.

^II-3 Bull. U.S. Geol. Survey. No. 31 p. 104.

^II-4 Scudder. Pretertiary Insects p. 319, 320.

^II-5 Zittle. Traite de Paleontologie t. II. and in Bull. U.S. Geol. Survey No. 31.

^II-6 It would be presumptuous for one who has studied the palaeozoic insects so little as I have done to criticize the accepted classification of them. I therefore quote it without change, although it does seem to me that ordinal distinctions arose earlier than indicated by Mr. Scudder.

^II-7 We find here an intermembral homology analogous to that which exists between the fore and hind limbs of Vertebrates. See an exhaustive paper by Wilder on Intermembral Homologies, Proc. Bost. Soc. of Nat. Hist. vol. XIV, p. 154.

^II-8 In fact I do not believe that the living May-flies are so primitive as regards their wing structure as has been commonly supposed. They have attained a high degree of cephalization of the function of flight, as shown by the reduction in size of the hind wings, and the large development of the mesothorax. The subcosta and radius are nearly parallel with the costa and closely approximated to it; the wings are well corrugated; and an extensive system of concave veins have been developed. Each of these characteristics is discussed later.

^II-9 Redtenbacher was not the first to recognize media as a principal vein. This was done by Edward Doubleday nearly fifty years ago. See his Remarks on the Genus Argynnis, Trans. Linn. Soc. Vol. XIX, 1845. I have adopted the term media in preference to discoidal vein proposed by Doubleday as the latter might be confused with discal vein, the term commonly applied to certain cross veins.