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POPULAR SCIENCE MONTHLY 



and easily floated by rains into streams and rivers, and thence carried 

 by currents into larger bodies of water, where permanent deposits are 

 accumulating. Both wings and molts are fairly resistant to decay, 

 and thus more readily preserved than are the softer parts of the body. 

 Such molts have been found in this country from the Coal Measures at 

 Mazon Creek, Illinois; from the Upper Coal Measures of Eastern 



Fig. 4. Hind wiDg ot 



Carboniferous cockroach, Fig. 6 Hind wing of a 



Promylaeris rigida Scud- Fig. 5. Hind wing of a Per- modern cockroach, Ec- 



der. Twice natural size. mian cockroach, x ±. Orig- tobia germanina. Orig- 



Author's illustration. inal drawing. iual drawing. 



The conspicuous changes in the hind wing as seen here are increased expanse of the anal 

 area, increased proportionate breadth of the wing, origin and development of a longitudinal 

 fold, development of plications in the folded area of the wing, development of cross veins. 



Kansas; and from the Permian of Central Kansas. Eecently an in- 

 teresting specimen, shown in the accompanying illustration, has come 

 to light from the Coal Measures of Clinton, Missouri. 1 A few speci- 

 mens have also been obtained from the coal formation of Scotland. 

 The young of Paleozoic cockroaches closely resemble the adults, and 

 were evidently in form and habits very similar to young cockroaches of 

 the present day. 



The cockroaches of Carboniferous time are, on a general average, 

 larger than those of later time. The largest described form, Archo- 

 blattina Beecheri Sellards, has a body, exclusive of the head, three 

 and one half inches long, with an expanse of wings of six and one 

 fourth inches. The Permian forms, and, also, those from mesozoic 

 and later formations, are, so far as known, smaller than those of the 

 Carboniferous. 



There appears to be no authentic record of the occurrence of cock- 



1 Collected by Dr. J. H. Britts and transmitted by him to the National 

 Museum. Kindly submitted to the writer for illustration by Dr. David White. 



