1870.J HUNT — ON LAURENTIAN ROCKS. 9 



in them the Eozoon. This notice, which appeared in September 

 in a Newburyport journal, is reproduced in the American Natu- 

 ralist for November. My own specimens collected in August last 

 near Newburyport, at the locality known as the Devil's Den, jiid 

 not, however, furnish any traces of Eozoon, and I may here remark 

 that I had already, so long ago as 1864, caused slices to be made 

 of a specimen of limestone from that locality, which were then 

 examined by Dr. Dawson with negative results. In November, 

 however, Mr. Bickoell visited Newburyport and got from a quarry, 

 about a quarter of a mile distant from the place just mentioned, 

 specimens of a serpentinic limestone in which he again found 

 Eozoon. Slices which he has kindly sent me have also been 

 examined by Dr. Dawson, who confirms Mr. Bicknell's observa- 

 tion, and finds in them Eozoon Canaderise, though fragmentary 

 and not very well preserved. The tubuli, as in the specimens 

 from Grenville, are injected with serpentine, and may be seen on 

 etched surfaces as well as in transparent slices. A crystalline 

 mineral is however abundantly disseminated in the limestone, and 

 unskilled observers might have difiiculty in recognizing the 

 fossil. 



Another locality, about twenty-eight miles to the south-westward 

 of Newburyport, has however, afi"orded me much better specimens. 

 In company with Mr. L. S. Burbank of Lowell, a zealous and 

 successful teacher of geology and mineralogy, I visited in October 

 last the limestone quarries of Chelmsford, some five miles from 

 Lowell. This limestone and its accompanying gneiss closely 

 resemble the Laurentian rocks of other regions, and scapolite, 

 apatite and serpentine occur as associated minerals, though the 

 latter was rare in the quarries then visited. A few days after- 

 ward Mr. Burbank kindly sent me specimens of a mixture of 

 limestone and yellowish-green serpentine from another quarry in 

 the vicinity, which I had been unable to visit, and these have 

 proved to be rich in Eozoon Canadense. The continuous and 

 complete calcareous skeleton of the fossil does not appear in these 

 specimens, which seem like some portions of the rock from Gren- 

 ville, as described by Sir W. E. Logan, to be made up of 

 fragments of the calcareous shell of Eozoon, mingled with grains 

 of serpentine, and cemented by crystalline carbonate of lime. In 

 the specimens from Grenville, and from most other localities, the 

 mineral matter replacing the sarcode and filling up the canals and 

 tubuli in the calcareous Eozoon skeleton, is generally serpentine 



