so. 1441. AMEMICAN PALEOZOIC INSECTS— HANDLIRSf '11. 717 



consider it Aviser for the present to separate them than to unite them 

 Avith uncertainty. 



In the establishment of families I have allowed myself to be gov- 

 erned I)}- chronogenesis, taking- those forms which most nearly 

 approach the protoblattoids, namely, the palaeodictyopteran type, as 

 the stem group. This group includes, among others, the genus ArvJii- 

 iinjlacris Scudder, which, being the first described, I use in the family 

 name '' Archimylacridse."' This family embraces the large majority' 

 of Paleozoic forms, and scarcely continues into the ^lesozoic; it like- 

 wise includes the olde><t forms. All other families — and among these 

 the inylacrids also, whicli were previoush^ regarded as a stem group — 

 are more highly specialized and may l)e traced back to the archimyla- 

 crid type. They appear chiefly in later strata and several of them 

 pass over into the Mesozoic. 



If, with Scudder and Sellards, we should regard the mylacrids as 

 the most primitive blattoids, we should then be forced to go much 

 further, and consider the blattoids the most primitive insects; then 

 the archim3'lacrid wing would form the connection with the Paheodic- 

 tyoptera, wdiich, how^ever, in all points are incomparably more prim- 

 itive forms and are also proved to be decidedly older than the myla- 

 crids and the blattoids in general. 



It is not possi])le to derive the blattoids from more highly special- 

 ized orthopteran forms, as the locustids, etc. ; and even if elongated 

 ovipositors should actually have been present in some lilattoids, 

 which I, however, cpiestion, there would still ])e no groiuid for such 

 an acceptation, because, as is well known, similar structures occur in 

 the most diverse developmental series, and were also present in many 

 Pahvodictyoptera. The fact is that in those old beds in which as yet 

 no blattoids have been discovered, no true Orthoptera have likewise 

 been met with, but only PalBeodictj^optera. In the ver}^ oldest forms, 

 cross veins are always present. A disappearance of cross veins always 

 indicates a higher specialization, and in the bhittids is frequently 

 associated with a stronger chitinization of the front w ing. 



Family ARCHIMYLACRID.E, new family. 



This group embraces the large majority of Paleozoic blattoids, and 

 is united with the proto})lattoids, namely, the Paheodictyoptera, by 

 transitional forms. The neuration of the Archimylacrida? mainly 

 resembles the pal^eodictj^opteran t3'pe, and may be regarded as the 

 point of origin for the succeeding more highly specialized families. 



The subcosta of the front wing is always preserved as an independent 

 vein and sends otf a variously large number of branches to the costal 

 margin. These offshoots are either equalh' divided (pectinate) or are 

 united in groups, but never issue in a raylike manner from one point 

 at the base of the wing. The subcosta is never restricted to a short, 



