Knight.] 190 [April 19, 



Wyman had found the same structure in the teeth of a 

 recent fish, the Lepidosteus (Gar pike of the Western rivers), 

 but not quite so complicated in arrangement. 



Mr. L. S. Burbank, of Lowell, who was present by invita- 

 tion, gave the following views on the Eozoonal limestones of 

 eastern Massachusetts : — 



The observations, the results of which are here presented, relate 

 chiefly to those deposits of crystalline limestone, that occur in the 

 band of granitic gneiss which extends in a south-westerly direction 

 from near the mouth of the Merrimack River through the entire 

 breadth of the State. 



To this formation belong the so-called granites of Westford and 

 Chelmsford, which are extensively quarried for building purposes. 

 In many other places also the gneiss of this series is highly crystal- 

 line and not readily distinguished by its mineralogical character from 

 a true granite. 



This belt of gneiss is bounded on the northwest by the slates of 

 the Merrimack and Nashua vallies, which apparently rest conform- 

 ably upon it. Moreover, there appears to be a gradual transition in 

 passing westward, from the coarsely crystalline gneiss, through mica 

 and hornblende schists, to the thin bedded clay slates like the roof- 

 ing slate of Lancaster. It may also be observed, especially in the 

 vicinity of Lowell and Chelmsford, that the coarser granitoid gneiss 

 occurs in beds alternating with the thin bedded and fine grained mica 

 and hornblende slates ; while these latter pass by insensible grada- 

 tions into a clay state. 



From a series of careful observations on these rocks, I am con- 

 vinced that the slates above referred to cannot be separated from 

 the underlying gneiss, but form with it a continuous series ; the whole 

 apparently underlying the great gneissic formation that stretches 

 across the State from north to south, through the central and west- 

 ern part of Worcester County, and which includes the rocks of Wa- 

 chusett mountain and the adjacent highlands. 



Soon after the discovery of Eozoon Canadense by Mr. Bicknell, 

 in the serpentine limestone of Newbury, it was also identified by Dr. 

 Dawson in specimens collected by me at Chelmsford; as noticed by 

 Dr. Hunt in the American Journal of Science for January, 1870. 

 The specimens then examined were not from the rock in place, but 

 were obtained from some outlying masses near one of the quarries. 



