766 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxix. 



(SPILOBLATTINIDiEi species. (Abdomen.) 

 Spiloblatlina sp. Sellards, Amer. Jour. Sei. (4), XVIII, 1904, p. 133, fig. 22. 



L(Ku/ify. — La wi Slice, Kansas. Uppei- Coal Measures; Le Roy 

 (Lawrence) shales. 



Family MYLACRID^E Scudder. 



Front wing of very variable shape, but generally broad and short; 

 nearly always widest at the base. Costal area always of a more or less 

 triangular form, never band-shaped; the veins never arranged in a 

 regularly pectinate manner on the subcosta, but the main ones alwaj's 

 issue radially from one point. The radius, as a rule, sends numerous 

 branches anteriorly or it divides into 2 widely l)ranched, principal oii*- 

 shoots. The media gives off its branches either seriall}^ from one stem 

 backward, or it forms 2 compound main branches or (more rarely) the 

 offshoots are directed forward. Cubitus with a very variable number 

 of veinlets branching off' posteriorly. Anal area chiefly rather large, 

 its veins never or but quite exceptionally ending in the anal fold, but 

 in the posterior border. The structure is more or less fine-grained 

 leathery, often more cross wrinkled. Regular cross veins as well as 

 borders to the veins were not observed. The bod}" was very ])road 

 and flat. 



I regard the Mylacridw, which occur principally in the Middle and 

 Upper Carboniferous formations of North America, as an extremely 

 developed lateral branch of the blattid series, which probably branched 

 off very early, and consequently^ in many respects has still preserved 

 rather primitive characters; for instance, the structure of the media 

 in the majority of forms. Perhaps the}' owe their origin to an adap- 

 tation to their environment, for it is remarkable how similar many of 

 them are to certain leaves of ferns, with which they are generally 

 found (to which fact Scudder has alread}' called attention). Probably 

 they lived under deciduous fern fronds, and by their similarity to the 

 pinnge were protected from their enemies. 



HEMiMYLACRIS, new genus. 



This genus could be almost as well referred to the archimylacrids. 

 The costal area is broad; in one species almost quite triangular; in the 

 others, still somewhat band-shaped; the branches of the subcosta issue 

 in part from one point, in part from the subcosta, so that there is a 

 choice between the two families mentioned. The radius sends 4 

 branches forward, the first of which separates into 2 or 3 twigs. The 

 3 offshoots of the media are directed backward to the apical and inner 

 borders, and the -i or 5 branches of the cubitus do not take up the 

 entire free portion of the posterior margin. The anal area extends 

 over about two-fifths the length of the wing, and is more than twice 



