Mr. S. H. Scudder on Devonian Insects. 255 



Fig. 5. Median part of radula (magnified). 



Fig. 6. Lateral part of radula. 



Fig. 7. Marginal part of radula. 



Fig. 8. Mandible (magnified). 



Fig. 9. Reproductive organs, hg, hermaphrodite gland ; e, its efferent 

 duct ; alb, albuminiferous gland ; od, oviduct (prostatic por- 

 tion) ; od', oviduct (infraprostatic portion) ; sp, spermatheca ; 

 vd, vas deferens ; jje, penis; v, vestibide. 



Figs. 10, 11. Shell (magnified). 



XXIII. — Relation of Devonian Insects to Later and Existing 

 Types. By Samuel H. Scudder*. 



It only remains to sum up the results of this reexamination 

 of the Devonian insects, and especially to discuss their rela- 

 tion to later or now existing types. This may best be done 

 by a separate consideration of the following points : — 



1. There is nothing in the structure of these earliest-known 

 insects to interfere with a former conclusion f that the general 

 type of wing-structure has remained unaltered frorn the earliest 

 times. Three of these six insects [Gerephemera, Homothetus^ 

 and Xenoneura) have been shown to possess a very peculiar 

 neuration, dissimilar to both Carboniferous and modern 

 types. As will also be shown under the tenth head, the dis- 

 similarity of structure of all the Devonian insects is much 

 greater than would be anticipated ; yet all the features of 

 neuration can be brought into perfect harmony with the 

 system laid down by Heer. 



2. These earliest insects were Hexapods^ and, as far as the 

 record goes, preceded in time both Arachnids and Myriopods. 

 This is shown only by the wings, which in all known insects 

 belong only to Hexapods, and in the nature of things prove 

 the earlier apparition of that group. This, however, is so 

 improbable on any hypothesis, that we must conclude the 

 record to be defective. 



3. They were all lower Heterometabola. As wings are the 

 only parts preserved, we cannot tell from the remains them- 

 selves whether they belong to sucking or to biting insects ; 

 for, as was shown in the essay already referred to, this point 

 must be considered undetermined concerning many of the 

 older insects until more complete remains are discovered. 



* From the ' American Journal of Science,' Feb. 1881. 



This summary of results is the conclusion of a memoir by Mr. Scud- 

 der " On the Devonian Insects of New Brunswick," published in the 

 ' Anniversary Memoirs of the Boston Society of Natural History,' 1880. 



t " The Early Types of Insects," Mem. Bost. Soc. Nat. Hist. iii. p. 21. 



