258 On Triassic Insects from the Rocky Mountains. 



paucity of data, the Upper Palaiozoic aspect of the few vege- 

 table remains from Playfair can have but a negative value 

 beside the positive proof of the alliance of the insects to 

 Mesozoic forms. Of Triassic insects our knowledge is ex- 

 ceedingly meagre ; a single neuropterous larva from the Con- 

 necticut valley is all that the formation has hitherto yielded 

 in this country. In Europe we knoAv of only four species, 

 each, I believe, from a single specimen ; one of these is a 

 cockroach, but it is entirely different from any of the Fair- 

 play species, and indeed from any other known forms, so that 

 we get no light from this quarter. 



It may be urged that, as much the larger proportion of 

 known Palgeozoic cockroaches come from Europe, our own 

 fauna being comparatively un worked, this discovery may only 

 indicate for America an earlier advance within Palseozoic 

 times toward later types. Besides the important considera- 

 tion that this would be in direct opposition to what we know 

 of subsequent periods in America, there are only two facts 

 known to me among fossil insects bearing upon this point, 

 one in favour of this hypotliesis, the other against it. The 

 first is the recent discovery in beds at Kansas City, Mo., said 

 by the State geologists to have 800 feet of Carboniferous rocks 

 above them, of the wing of a heteropterous Hemipteron, which 

 I have called Phthanocoris. In Europe no instance is re- 

 corded of any insect belonging to this great group of Hemi- 

 ptera in Pala30zoic rocks, the three or four Hemiptera so far 

 found belonging to the homopterous division. The other fact 

 is brouglit forward in my memoir on Palajozoic cockroaches, 

 and is of far more importance, not only because it is of broader 

 significance, but also because it is drawn from the same group 

 as that under discussion. The Palgeoblattarise are divisible 

 into two groups, the Mylacridse and the Blattinarias, the 

 former of which is in point of structure the more primitive 

 type. Now the Mylacridae occur only in America, and form 

 indeed about two thirds of the species known from this con- 

 tinent. In Carboniferous times, therefore, as regards cock- 

 roaches, America was more old-fashioned than Europe, and 

 we should look for the introduction of new elements earlier 

 in Europe than in America ; yet the better explored Carbo- 

 niferous and Permian deposits of that continent have yielded 

 no traces of anything akin to the Fairplay insects. The first 

 appearance of any such is in Mesozoic strata, and notably in 

 the Lias. 



So far as I know this is the first attempt to determine the 

 age of a deposit from its insect-remains alone, and it is un- 

 fortunate for its acceptance by naturalists that the plants give 



