140 



been found in Laurentian, Huronian and Taconian limestones, 1 

 those believing in its organic origin must admit that the animal 

 producing it had a very long range in time. 



GENERAL RELATIONS OF THE MONTALBAN ROCKS. 



The considerations supporting the view that the rocks de- 

 scribed in the preceding pages, and designated as Montalban, 

 are newer than the Huronian system ; and that, like the Huro- 

 nian rocks, they constitute a series which may be characterized 

 as both lithologic and chronologic, fall naturally under two 

 distinct heads: (1) Lithologic; (2) Stratigraphic. The 

 lithologic evidence will be considered first. 



No one familiar with these rocks as they occur in the field 

 will require further proof of the connection of the exotic and 

 indigenous granites with the gneiss. That the gneisses are 

 frequently granitoid, — i.e., coarse, crystalline, and apparently 

 unstratified, — and that the indigenous granite thus resulting 

 exhibits frequent transitions into undoubted exotic granite, are 

 among the most patent and often-recurring facts in the geology 

 of this region. If this is the true relation of the granite and 

 gneiss, then it were reasonable to suppose that the granite 

 has been derived mainly from the more ancient and lower 

 portions of the gneiss ; and that, where the granite has expe- 

 rienced little or no extravasation, it should be found to-day 

 occupying the stratigraphic and geographic position of the 

 gneiss which it represents. Now, leaving out of view the 

 endogenous granite, — which, of course, was deposited subse- 

 quently to the gneiss , — it cannot be questioned that the 



1 The Eozoon canadense. has been reported by competent observers as occurring in the 

 Laurentian limestones of Canada, New York, Bavaria, etc. ; in the Huronian limestone 

 of Newbury, Mass.; in the Montalban limestone of Chelmsford and Bolton, Mass.; 

 and in the limestone in Hastings County, Canada, which Dr. T. Sterry Hunt has 

 recently assigned to the Taconian (see Second Geological Survey of Pennsylvania, vol. 

 E, pt. 1, pp. 171, 177, and 241). While Mr. R. J. Lechmere Guppy (Quart. Journ. 

 Geol. Soo. Lond., xxvi, 413-414) has given the name of Eozoon caribbaum to a sup- 

 posed organism found by him in the Caribbean series of the island of Trinidad; a group 

 of semi-crystalline beds which the present writer has correlated provisionally with the 

 Taconian of Berkshire County, Mass. (Proc. Bost. Soc. Nat. Hist., xx., 55.) 



