OF THE PAST. 213 



of this repetition of the style of branching of the mediastinal 

 and anal offshoots by the scapular and internornedian respec- 

 tively. 



V 



A certain amount of geological evidence may also be claimed 

 in support of this view. A survey of the species of the two 

 groups found up to the present time in America, published and 

 unpublished, shows that all the Mylacridce are found below the 

 Upper Carboniferous, while more than half the Blattinarue are 

 found in or above it. This results largely from a recent and 

 as yet unpublished discovery of Blattinarice in the Upper Coal 

 Measures of Ohio and "West Virginia, which in their general 

 features are much nearer than previously discovered American 

 Cockroaches to the European Blattinarice, the latter of which 

 come generally from Upper Carboniferous beds. The Mylaerida 

 have therefore been found in America in strata generally 

 regarded as older than those which in Europe have yielded 

 Cockroaches, and this gives a sufficient explanation why no 

 MylacridcB have yet been found in the Old World. In America 

 one is mostly dealing with absolutely older forms, and they 

 naturally give that continent a more old-fashioned look, when 

 we regard the Carboniferous fauna as a whole. As already 

 stated, a wing from the French Silurian (Pakeobfattma Dounlki 

 Brongn.) has been claimed as a Cockroach, but without good 

 reason, and to see a real old Cockroach one must look to 

 America, 



Up to this point we have contrasted the palaeozoic Cockroaches 

 with the existing forms only, and finding such important dis- 

 tinctions between them, we naturally turn with some curiosity 

 to the intermediate mesozoic and tertiary formations. 



tt 



Now, not only are the mesozoic species as numerous (actually, 

 but not relatively) as the palaeozoic, but a recent discovery of a 

 Triassic fauna of considerable extent, in the elevated parks of 

 Colorado, presents us with a series of intermediate forms 

 between those peculiar to the Coal Measures and those charac- 

 teristic of the later mesozoic rocks. Excluding, however, for a 

 moment this Triassic fauna, we may say of the later mesozoic 

 species that they are Neoblattarice, not Palceoblattarice, though 

 they still show some lingering characteristics of their ancestry. 

 Thus the front wings are in general of a less dense texture than 





