254 PROCEEDINGS OF THE ACADEMY OF [May, 



22. The Number of Anal Cross-veins. — Progressive petiolation 

 reduces the area available for anal cross-veins, but not always to the 

 extent one might expect. Thus of American genera discussed in this 

 paper which have the petiolation extending distad to the arculus, 

 Paraphlehia has 2, PhUogenia 0, Dimeragrion 1 or 0, Lithagrion 

 anal cross-veins. Calopteryginae (Selys) have on the whole more 

 anal cross-veins than do the Agrioninse Selys. If the latter are 

 descendants of some of the former and if Tarsophlehia stands in an 

 ancestral position to the Zygoptera, then we may consider reduc- 

 tion in number of the anal cross-veins as a specialization. Proto- 

 myrmeleon, Tarsophlehia, Isophlebia, and Anisophlebia each had not 

 less than four anal cross-veins, some of them many more. In 

 Euphceopsis they are not preserved, in Steleopteron they appear to 

 have been present only distad to the level of the outer (distal) end 

 of the quadrilateral. 



B. The characters included under group B on p. 245, ajited, are 

 Nos. 7, 8, 10, 12, 156, 176, 19, and 20. In the comparisons made in 

 the early pages of this paper, these characters have been stated in 

 terms of numbers of rows of cells found between the branches of the 

 great veins. They may be stated also by specifying the number of 

 interposed, or supplementary, sectors in each area, and have usually 

 been so stated in the taxonomic literature. It is easy to translate 

 one method of statement into the other, as one row of cells implies 

 no supplementary sector, two rows of cells one supplementary sector, 

 three rows two sectors, etc. The individual variation to which they 

 are subject increases as the hind margin of the wing is approached. 



The Protodonate wing of the Carboniferous and the Permian was 

 richly veined with many supplementary sectors. So also were the 

 Odonate wdngs of the Lias, excepting Protomyrmeleon; if Handlirsch's 

 interpretation of its venation be correct,*^ there was but one row of 

 cells between each of the branches of the main veins, except between 

 Rs and Ms (two rows increasing to three), Ms and M4 (two rows), 

 M4 and Cui (two rows), and posterior to A (two rows). 



Turning to the Odonata of the Jura,*" we find richly veined wings 

 in the Anisozygoptera {Tarsophlehia, Stenophlebia, Isophlebia, 

 Anisophlebia), and in Euphceopsis; Steleopteron has one row of cells 

 between Mi and Mio, Mio and M2, M2 and Rs, INIs and M4, and be- 

 tween the veins posterior to Cui, three rows between Rs and Ms, two 

 rows between M* and Cui. 



85 Foss. Ins., Taf. XLII, fig. 14. 



8« Handlirsch, Foss. Ins., Taf. XLVII. 



