104 University of California Puhlications. [Entomology 



than the venation characters in the groups just considered. 



The venations are all comparatively simple, but quite variable 



as to number of veins. In 

 the accompanying diagram 

 (Fig. 40), the venation shown 

 at the anal angle does not 

 fairly represent this region 



FIG. 40. Venation of Gerarina. Thedot- • 'ii ,| incjpptci nlnopd in 



ted lines sliovv the veins that are some- m ail tne inseciS piaceu in 



times absent. ^j^^g family; but accuracy 



on this point is impossible at present, because of the frag- 

 mentary character of the specimens. 



PLATYPTERID.E. 



This group of Paleozoic insects, as defined by Brongniart, 

 includes the genus Lithomantis, placed by Scudder in Hemer- 

 istina, and a large number of similar many-veined forriis which 

 usually have dense reticulated veins, something after the order 

 Stenodictyopteridse, but not so dense nor with very numerous 

 close-lying longitudinal veins. It will not be necessary to 

 figure the venation, as it is not essentially different from 

 Paleoperinse or Hemeristina. Brongniart compares these 

 insects with the Sialidae. 



protOperla. 



The insects placed in this group by Brongniart seem to 

 belong to Scudder's Hemeristina. They possess a primitive, 

 and somewhat reduced, venation, and might easily present an 

 ancestral form of the Perlida?. They show no specific character, 

 however, that will afford undoubted evidence of this relation- 

 ship. This is perhaps what should be expected, since the vena- 

 tion in the Perlid« is of such an undifferentiated character. 



PERLID^E. 



The Perlidje possess two pairs of independent wings lying 

 over each other and flat on the back when at rest. The front 

 wings thus in a measure serve as a protection for the rather 

 more delicate, and usually distinctly broader, folded hind 

 wings. In one case, Nemura trifasciata, the front wings have 

 become reduced to a semi-rudimentary condition, giving the 

 insect somewhat the appearance of certain Cerambycida^ with 

 abbreviated elytra. 



