40 S. H. SCUDDER ON PALAEOZOIC COCKROACHES. 



PALAEOBLATTARIAE. 



Palaeozoic cockroaches ; in which the fore wings are diaphanous, generally reticulated 

 and nearly symmetrical on either side of a longitudinal middle line; the externomedian 

 vein is completely developed and divides in the outer half of the wing, its hranches gener- 

 ally occupying the apical margin. The internomedian area is broad at its base (beyond the 

 anal area), rapidly tapers apically and is filled with oblique, mostly parallel veins, having 

 nearly the same direction as the anal veins, which, like them, strike the inner margin. 



Their bodies appear to have been flat, but slenderer than usual in cockroaches of the 

 present day, the pronotal shield depressed, more or less elliptical, but sometimes longer than 

 broad, the head partly concealed by it as in living types. They were of large size; but 

 while the average was considerably above that of existing cockroaches 1 none were much 

 larger than some S. American species of Blabera. Germar was the first to note the 

 diaphaneity of the fore wings, 2 and Goldenberg the presence of the externomedian vein, 8 

 and the course of the anal branches. 4 



Mylacridae. 



In this group the mediastinal vein of the tegmina with its branches consists of a number 

 of veins, simple or forked close to their origin, spreading in a fan shape and appearing to 

 arise from a single point or near a single point close to the base of the wing ; or in other 

 words, the branches originate from the main vein close to its base and to each other, the 

 outermost being much longer than the innermost, often double as long as it, and either 

 straight or uniformly arcuate; the area of the vein is thus triangular and more or less than 

 half as long as the wing. The character of the vein therefore much more nearly 

 resembles that of the anal vein than of the others. The group is confined, geographically, 

 to America, and the wings are a little stouter on the average than those of the Blattinariae, 

 the breadth being usually contained in the length less than two and one half times. 



Mylacris (/wXazpit;). 

 Mylacris Scudd., in Worth. Geol. Surv. HI. in., 568-69 (1868). 



The mediastinal vein of the upper wing consists of about five principal stems, two or 

 three of which fork before the middle, all of them straight or very gently curved, the 

 outermost extending half way or even more to the tip of the wing; the point from which 

 the principal stems originate is either in the middle of the wing or nearer its inner than 

 its costal margin. The scapular vein is always arched strongly at the base before branching, 

 which it commences to do as soon as allowed by the branches of the mediastinal vein ; it 

 then runs subparallel to the costal margin always to the extreme tip of the wing; during 

 the larger part at least of its course it runs very nearly along the middle line of the wing. 



1 The average length of the front wing appears to have . . . wodurch das Mittelfeld in eine ausseres und ein inneres 

 been about 2G mm. Mittelfeld getheilt wird. Goldenberg, Palaeontogr. iv, 



2 Der deutliche Aderverlauf, den wir . . . wahrnehmen, 20-21. 



zeigt nns daher, (hiss diese vorweltliehen Arten pergament- 4 l'»-i den Blatten der Jetzwelt miinden die Adern dieses 



arlige Oberfliigel besassen. Germar, Verst. Steink. Wet- Hinterfeldes [anal field] theilweise in die Begreuzungsader 



tin, 82. [anal furrow] desselben, w'ahrend bei den Lias- und Kohlen- 



3 Beijenen [lebenden Blatten] lasst sich in diesem Felde blatten sammtliche Adern dieses Feldes in den Nahtrand 

 nur eine sich stark verastelnde Mittelader wahrnehmen, [inner margin] auslaufen. Goldenberg, Palaeontogr. iv, 20. 

 w'ahrend die Kohlenblatten hier zwei Mitfeladern zeigen 



