ISO 



SAMUEL H. SCUDDEE ON THE 



and scapular, and anal veins falling on the inner margin (some species of Scutinoblattiua) ; 

 and finally, similarly thickened wings with blended mediastinal and scapular, and anal veins 

 impinging on the anal furrow (other species of Scutinoblattiua). 



GEOGRAPHICAL DISTRIBUTION OF THE GENERA OF FOSSIL COCKROACHES. 



No one can handle many Palœozoic cockroaches without being struck by the fact that 

 they are of large size. I drew attention to this in 1879, remarking that "while the average 

 was considerably above that of existing cockroaches, none were much larger than some 

 South American species of Blabera," whose fore wings sometimes attain a length of sixty 

 to seventy millimetres. But I have now seen a fragment of a fore wing, which when per- 

 fect must have measured eighty millimetres in length. In an estimate from the then known 

 species of Palœozoic cockroaches I stated that " the average length of the front wing appears 

 to have been about twenty-six millimetres." 



Since then the increase in the number of species in this country has been largely from 



the younger Palœozoic rocks, and if we were to add the Triassic Palseoblattarite, of still 



smaller size, we should find that the average length of the fore wing in ancient American 



cockroaches, one hundred and thirty-three species in all, was 23 '2 mm. The Mylacridse 



