4 SCUDDER ON THE DEVONIAN 



The specimens discovered were six in number, some of them with their reverses. 

 They are now in the museums of tlie natural history societies of St. John, N. B. 

 and Boston, Mass. I am mucli indebted to Mr. G. F. Matthew, of the former institution, 

 and to Professor A. Hyatt of the latter, for the opportunity of studying these specimens 

 anew at my leisure. 



The plan of the present paper will be seen by a glance at the table above. As 

 the simpler devonian insects, first described, have certain special relations with the 

 Ephemeridae, their description is preceded by an account of the wing structure of 

 the modern May-flies, as a basis of comparison ; each of the devonian species is then 

 separately described, and its affinities discussed, and the whole is followed by a general 

 summary. The stratigraphical question being, in this instance, of special importance. 

 Principal Dawson has kindly prepared for me a statement of the case with which 

 the article closes.^ 



II. The Structure of the wings in Ephemeridae ; with a note on a jurassic 



SPECIES. 



The following statement considers mainly the direction and division of each of the 

 principal veins, and the comparative areas covered by them. 



The marginal vein forms the costal border. Tlie mediastinal vein is absent or, perhaps, 

 amalgamated with the scapular in Lachlania, Oligoneuria and Tricorythus ; in all 

 others it is simple, and extends to, or almost to, the tip of the wing, keejiing 

 at a very short and nearly uniform distance from the margin, with which it is generally 

 connected, especially on the apical half of the wing, by frequent cross veins. On 

 the basal half, the cross veins may be as abundant as apically, but they are generally 

 rarer, and may be entirely absent, even when frequent apically ; or they may be absent 

 throughout. In very rare instances, as in Coloburus, an intercalary vein may be 

 found in the apical half of the wing between this vein and the costal margin. 



The scapular vein is simple, and reaches the tip of the wing, excepting in the 

 three genera mentioned above, where it may perhaps be said to be amalgamated 

 with the mediastinal, as shown by its forking near the middle of the wing in 

 Tricoiythus ; in Lachlania, however, it terminates not at the tip, which possesses 

 only the marginal vein, but near the middle of the costal border. It is always 

 connected with the vein below by a greater or less number of, usually many, cross veins. 



The externomedian vein is always compound, and always covers at least half, usually 

 much the greater part of the wing. It always divides at the very base, and the upper 

 branch is always forked, while the lower may, although rarely, remain single, and is 

 usually forked to a less extent than the upper branch. Three is, therefore, the 

 smallest number of nervules which may reach the margin in the area covered by 



1 Besides the references given in the bibliography under Dawson's Acadian Geology, ■2d ed., pp. 513-23. 8vo. London, 



each species, notices of the devonian insects will be found 1868. Darwin, Descent of man, I, 360. 12mo., London, 1871. 



in the following places: Hartt, on the Devonian plant- Stett. Ent. Zeit., xxviil, lib-53, passim. Trans. Entom. 



locality of the Fern Ledges, Lancaster, N.B., in Bailey's Ob- Soc. Lond., 1871, 38-40. American Naturalist I, 445, 625- 



servations on the Geology of Southern New Brunswick, pp. 26. Proc. Boston Soc. Nat. Hist., X, 96, XI, 150-51_ 



131-40. 8vo., Fredericton, 1865; reprinted in substance, in Memoirs Boston Soc. Nat. Hist. HI, 13-21, passim. 



