THE PALEONTOLOGICAL DATA 



99 



was a variable number of accessory veins. But the fact that there was 

 no regularity in the position and niimbcr of these accessory veins indi- 

 cates that they were not of Sc 



fundamental importance ■'^',^■=^^^^'^^^^7^^^^^ — ~~~~ 



and could not be included j^^ /^'^l^^^^^^S-^^^P^^'^^ '^^ ~~^~^ 

 in a diagram representing 7^3 ( ^^,^-;;^^^^^^^^^^^^^^^^J^^ /<A "^ 

 the primitive type of branch- R^-^^'^ ^- '^^^^^^x^^^^^^^^^^^^^z^ 

 mg 01 the wmg-vems. i^^* "'^^-^r'^'^^-^''"^^^--^ y/y 



The evolution of the yjf^^^'^-^-.^i^r^^SM^i^^^^— ^^ 



media. — In the case of Fig- 93- — Pseudofouqiiea camhrensis (After 



J. ... 1 Handlirsch). 



media it is much more 



difficult to determine the primitive type of branching. A study of recent 



forms led Comstock and Needham to conclude that the primitive media was 



four branched and that the branching was dichotomous. Regarding this 



we made the following statement : 



"The vein occupying the center of the wing is the media (M). In those 



orders in which it retains most nearly its primitive form it is usually three- 



-- - ^^ ^^""^ 



■'^ 



'A 



I cu. \ Cm r ^ 



Fig. 94. — Stygne Roemeri (After Handlirsch). 



branched; but the fact that in the more generalized members of several 

 widely separated orders it is four-branched leads us to believe that it was 

 four-branched in the stem form of winged insects. The branches are 

 designated as media-one (Mi), media-two {Mo), media-three (M3), and media- 

 four (M4), respectively." 



The following are examples of generalized forms among living insects 

 showing a four-branched media: 



*DlSTKIBUTION OF ACCESSORY VeINS IN THE LoWER UPTER CARBONIFEROUS INSECTS 



Fig. R.. R3 R4 Rs Ml M2 M3 M4 Cui Cu2 



Metropator pussillus 14 i i o 00 o o i o i 



Paolia vetusta 15 2 2 2 l 2 i 2 4 4+I 



Paolia Gurleyi 16 i 2 o o I o 3 o 3 o 



Camploroneura reticulata 17 



Bathytaptus falcepennis 18 2 o o o o o 



Eurythmoptcryx antiqua 19 i 00 00 o i 2 o 3 



Pseudofouquea cambrensis 20 i o o o o o i ? 



Stygne Roemeri fore w 3 o o o.i o 1 1 4 o 



hind w 21 ? o o o o I I 3 o 



