Geology and Mineralogy. 313 



the clearly ascertained species 220 are restricted to North 

 America, the remainder to Europe. Not a single species seems 

 to be common to two localities and of the 252 good genera only 

 11 are, common to America and Europe, all belonging to the 

 order Blattoidea. These are: Aphthoroblatlina, Asemoblatta, 

 Blattinopsis, Piety omylacr is, Eumorphoblatta, Olethroblatta, 

 Phyloblatta, Poroblattina, Syscioblatta, Sysciophlebia, and 

 Xenoblatta. In another publication, however, the author re- 

 marks : " In such groups as first exist in single individuals, no 

 sort of conclusion as to their actual horizontal distribution can 

 be obviously drawn, and it consequently follows that there is a 

 striking agreement in the Paleozoic fauna in both continents," 

 America and Europe. 



The ordinal evolution is as follows : The stem group of all 

 winged insects, Palaeodictyoptera, has 116 species. In these the 

 structure was of the simplest order, and they were apparently 

 without adaptation to the definite modes of life which we are 

 -accustomed lo see in nearly all existing insects. Out of these 

 were evolved all the higher orders of Hexapoda. The other 

 more prominent orders are : Protorthoptera (primitive Orthop- 

 tera, or locusts), with 43 good species ; Protoblattoidea (ancestors 

 of cockroaches and mantids), with 39; Blattoidea (cockroaches), 

 with 320 ; Protodonata (primitive Odonata, or dragon-flies), with 

 6, and Megasecoptera (ancestral panorpatids, or scorpion-flies), 

 with 18 species. But a single one of the Paleozoic orders, — 

 Blattoidea, passes into the Mesozoic. Many of these Carbon- 

 iferous insects attained considerable size, and some are known 

 much more than half a meter across the wings. 



Permian. — The climate at the beginning of the Permian is 

 thought to have been like that of the Carboniferous ; later it 

 changed remarkably, for in the Southern Hemisphere there was 

 then an extended glacial period across South America, Australia, 

 South Africa, and even to India. It also exerted its influence 

 upon the Northern Hemisphere, where the mild, damp Carboni- 

 ferous conditions passed at least locally into a desert climate. 



Our knowledge of the Permian insects is restricted to the 

 Upper Permian deposits of Russia and to the Lower Permian of 

 North America and Europe. The Fairplay, Colorado, beds, 

 which Scudder was disposed to regai'd as of Triassic age, the 

 present author regards as belonging to the Permian, as there is 

 nothing which in the least points to Triassic development. 



The Permian insects here described number 112 good species 

 in 45 genera, besides 36 poor ones. Nearly all the genera are 

 represented by one or two species, but Phyloblatta has 44 and 

 Sysciophlebia has 13 species. Of Carboniferous genera continued 

 into the Permian there are Phyloblatta, Sysciophlebia, Dicla- 

 doblatta, Poroblattina, and Nearoblatta. Of these the first two 

 genera are also common to North America and Europe. 



In the Permian there are none of the most primitive insects, 

 the Palaeodictyoptera, while the order Protorthoptera is repre- 



