with Descriptions of New Forms. 123 



sibly before, and is from that time on a distinct and continuous 

 line. The customary separation of the group into an older 

 and a newer part, — the Paleoblattidse and the Blattidse, while 

 in a sense artificial,, is nevertheless convenient as marking two 

 fairly distinct stages in the development of the phylum. The 

 two families are best included within a single super-family 

 characterized as follows, and for which the term Blattacea is 

 here suggested : 



Running Orthoptera ; body flat and carried close to the 

 ground ; tergum of the first thoracic segment (pronotum) 

 large, broad, typically shield-shaped ; head small, flat, inflexed, 

 capable of being more or less completely withdrawn beneath 

 the pronotum ; wings differentiated into a more or less thick 

 front wing, and a thinner, broader hind wing ; anal area of the 

 front wing marked off by a strong furrow ; hind wing not 

 folded in the earlier forms, folded in the later ; ovipositor 

 projecting from the abdomen in the Paleoblattidse, not, or but 

 slightly, projecting in the Blattidse. 



The geological range of the Blattacea is from the Carbon- 

 iferous to the present. Of the two families included, the 

 Paleoblattidse extend from middle or early Carboniferous to 

 the close of the paleozoic, possibly lasting over into early 

 mesozoic ; the Blattidse from late paleozoic or early mesozoic, 

 to the present. 



Paleoblattidce. 



Paleoblattariae Scudder, Mem. Boston Soc. Nat. Hist., vol. iii, p. 26, 1879. 

 Paleoblattidse Brongniart, Histoire des Insectes Fossiles, p. 416, 1894. 



The Paleoblattidse, the older and more primitive of the 

 Blattacea, are characterized as follows : 



Cockroaches with a well-developed and protruding oviposi- 

 tor. Eggs probably deposited singly in the ground, in stems, 

 or underneath the bark of trees. Hind wings not folded and 

 consequently lacking differentiation into a brownish resistant, 

 and a thin folded part. Anal area never plicated. Differenti- 

 ation in texture and venation between the front and hind 

 wings less marked than in the Blattidse, the front wings being, 

 as a rule, less coriaceous and the main veins in both wings more 

 nearly equally developed. Cross veins, except for the reticula- 

 tion of the membrane, are not common in the front wings, 

 and are unknown in the hind ones. 



Description of Genera and Species, including Nymphs. 



Mylacridm. 

 The Paleoblattidse are again subdivided into two subordi- 

 nate groups, the Mylacridse* and the Blattinarise. The former 



* The term Mylacridse in use for this group is misleading, since the ter- 

 mination is that accepted for family names. A better term is Mylacrinariee 

 to correspond with the coordinate division Blattinarise. 



