Description of an extinct paleozoic insect. 51 



Europe. Thus our Cambrian terrane includes the Lower Ordo- 

 vician, and we have no trace of the Upper Ordovician over a 

 large territory in eastern North America, including Acadia, and 

 most of New England. 



The next terrane includes the Silurian (Upper) and the Eo- 

 Devonian (Oriskany) and its deposits are spread over Acadia, 

 but not in an equal manner, some areas having been above 

 water through a considerable portion of the time when this 

 terrane was forming, and other portions, that were submerged 

 at the beginning, arose above the sea during its: progress. 

 Hence we find that in some areas the terrane begins with the 

 base of the Silurian (Medina and Clinton) and in others not 

 until the Eo-Devonian (Oriskany). The Lower Helderburgh 

 Fauna has not been recognized in this region, so that the groups 

 known by marine fossils are the Clinton, Niagara and Oriskany. 

 Throughout this terrane there are more or less of remains of a 

 flora which, we may surmise, originated on the great emerged 

 area of this part of the earth that was above the sea in later 

 Ordovician times. The first traces of it that we have are found 

 in beds of the age of the Clinton. It reaches its full measure in 

 the Niagara period, and continues to be repiesented by many of 

 the same species in the higher beds, thus extending up into the 

 Devonian. 



Great disturbances occurred after tlie Oriskany beds were 

 deposited, and the region was subjected to violent earth move- 

 ments, with intense pressure, and the eruption of granitic rocks. 

 The terrane which preceded or accompanied this time of disturb; 

 ance is the Upper Devonian, and consists of coarse conglomerates 

 and red slates ; in the conglomerates are fragments of Silurian 

 (Upper) corals, in the slates obscure remains of plants. 



Upon these Upper Devonian rocks, after their elevation and 

 folding, was laid down the Lower Carboniferous conglomerates 

 and shales containing a fauna and flora verj; diflferent from that 

 of the older time. The condition of the Carboniferous beds 

 indicates the removal of the pressure which had plicated and 

 altered the older rocks, though volcanic eruptions continued to 

 occur to a more limited extent. 



