54 



Hurouian system, or Green Mountain system. As re- 

 gards the limestones with Eozoon, from eastern Massa- 

 chusetts, which in the American Journal for Jan., 1870, 

 I referred to the more ancient Laurentian system. I 

 have in that same journal for July, 1870, pointed out the 

 fact that the Eozoon of Hastings coumVy, Ontario, occurs 

 in a series of crystalline schists which I consider newer 

 than the Hurouian, and the equivalent of the White 

 Mountain gneisses and mica-schists, so that, as I there re- 

 mark, "the presence of this fossil can no longer serve to 

 identify the Laurentian system. It will be remembered 

 that the Eozoon Bavaricum of Gumbel occurs in Bohe- 

 mia, in a series of crystalline schists above the Lauren- 

 tian, occupying probably the position of one or the other 

 newer systems just mentioned. I have in the American 

 Journal for last March (page 183), moreover, called at- 

 tention to the fact that the ciystalline limestones which 

 arc associated with the White Mountain or Terranovan 

 system in Maine, closely resemble in mineralogical char- 

 acters those of the Laurentian. It will therefore remain 

 for farther study, to determine how far the crystalline 

 limestones of eastern Massachusetts belong to the Lau- 

 rentian, and whether some of them are not included in 

 one or the other of the newer systems of crystalline 

 schists. The porphyry conglomerate noticed by the late 

 President Hitchcock and described by Prof. Hyatt, are 

 referred to in my paper of last October, mentioned 

 above. This rock is, I conceive, to be distinguished from 

 the old Hurouian porphyry, on which it often reposes, 

 and from the ruins of which it is derived. Similar con- 

 glomerate porphyries along the shores of the Bay of 

 Fundy appear to be of Upper Silurian age. 



