434 



NORTH AMERICAN INDEX FOSSILS. 



Mediastinal- 



Scapular- , 

 Ejctefnorrteoian; 



-^nal veins 



BLATTARi^. (Family PalcsohlattidcB Sellards), but Handlirsch and 

 others do not favor such a separation. 



Head often entirely concealed by the large shield-like pronotum. 

 In the winged cockroaches the front wings or tegmina are more 

 coriaceous than the hind wings and more generally preserved. The. 

 marked veins of the tegmen and wings are (Fig. 1737) : the sub- 

 costal or mediastinal, the radial 

 (including radial sector) or 

 scapular; the media or exter- 

 nomedian; the cubitus or inter- 

 nomedian, and the anal veins 

 separated from the rest by the 

 anal furrow. 



In the family Archimylacri- 

 d(E, which includes more than 

 one third of the American 

 species, the neuration still re- 

 sembles in the main the palseo- 

 dictyopteran type. The sub- 

 costa or mediastinal of the teg- 

 men is always preserved as an 

 independent vein sending off a 

 large number of branches to 

 the costal margin, either pectinate or united into groups, but never 

 issuing ray-like from the base of the wing; radius (scapular) more 

 or less copiously branched, separable into radius and radial sec- 

 tor only in the most primitive forms ; radial group divided into 

 clusters of twigs or branches all of which arise apparently on the 

 superior side of the principal vein ; media (externomedian) separated 

 into two main compound offshoots, or it forms one vein with branches 

 running off backwards, or finally, one such, with the branches 

 ramifying anteriorly; cubitus (internomedian) with numerous 

 branches to the inner margin, more rarely with an isolated widely 

 furcating superior offshoot; anal area always marked off by a 

 bow-shaped furrow, and containing a number of veins which fuse 

 on the posterior margin ; irregularly reticulate or delicately regular 

 cross-veins occur. Examples: Adeloblatta Columbiana (Scudder) 

 (Fig. 1738, b), and Asemoblatta mazona (Scudder) (Fig. 1737, 



Fig. 1737. One of the tegmina of 

 Etoblattina {Asemoblatla) mazona, X 2, 

 with the parts named. The areas are 

 marked along the margin, the veins are 

 named at the base of the tegmina. (After 

 Scudder. ) 



