FOSSILS. 451 



The ZapJirentis is a genus of Cyathophylloid corals, which are found sparingly in the 

 upper Silurian, but more abundantly in the Devonian series. The specimens from Lake 

 Memphremagog cannot be distinguished from specimens of the same genus from the 

 Eolian limestone in Sudbury. 



These fossils were examined by Prof. Hall, who pronounced them to belong to the upper 

 Helderberg group. The Atrypa reticularis, and certain species of Zaphrentis are com- 

 mon above division D of the Anticosti group, and the former is found in Lower Canada in 

 the extension of the Memphremagog rock, accompanied with other characteristic forms of 

 the upper Helderberg. The Canadian geologists, however, have not defined the limits of 

 the upper Helderberg upon this extension, in distinction from the Niagara group. 



The upper Helderberg, as seen on page 54, is in the lower part of the Devonian system. 

 It is better known to some as the Onondaga limestone. It is a remarkably persistent 

 group in its distribution, as it is often developed where both the shales above and the 

 sandstones below are wanting. How remarkable that this limestone can be recognized 

 among these azoic rocks ; and especially that it can be traced as far as Montpelier, in the 

 very heart of what, a few years ago, was universally conceded to belong to the oldest series 

 of strata upon the globe ! We confidently expect that the progress of knowledge will ere 

 long develop the age of every azoic rock in New England. 



