436 



NORTH AMERICAN INDEX FOSSILS. 



In the family Spiloblattinidce, with about 40 species from the 

 Conemaugh, and less than half that number from the Dunkard 

 formation, the interspaces between the main veins are remarkably 

 broad in the central portion of the tegmen, the costal area is always 

 band-shaped, and the branches of the subcosta arise successively 

 in a pectinate manner; the radius separates either into two widely 

 compound main branches, or it sends out forward a large number 



Fig. 1740, Mylacru anthracophila Scudder, X f > ^"d Orthomylacris antiqua 

 Scudder, both from the coal measures (Allegheny) of 111. 



of feebly compound offshoots; the media rarely divides into two 

 equally branched principal stems, but mostly forms a series of 

 branches running out forward ; cubitus and anal area as in preced- 

 ing family. Examples: Etoblattina (Dicladoblatta) tenuis Scud- 

 der (Fig. 1739, h), from the Conemaugh 

 formation of Ohio. Spiloblattina gardi- 

 neri Scudder, from the Permic of Fair- 

 play, Colorado. 



In the family Mylacridce which is repre- 

 sented by about 50 species in the Alleghany, 

 and perhaps half a dozen or more in the 

 Conemaugh and higher Coal Measures, the 

 front wing is of variable shape, but gen- 

 erally broad and short, nearly always 

 widest at the base. Costal area always 

 more or less triangular in form, never 

 band-shaped ; branches never pectinately 

 arranged on subcosta but main ones always 

 radial from one point; the radius as a rule sends numerous 

 branches anteriorly, or it divides into two widely branched 

 principal off-shoots ; the media gives off its branches either 



Mylacris an- 

 ( After Scud- 



