MINERALIZED WITH SILICATES. 63 
sent a delicate fibrous or tubulated appearance, as if they had 
moulded themselves on porous shells or very minutely-celled corals, 
spicules of sponges, &e. Shreds of corneous Polyparies, perhaps of 
Graptolites, abound in the matrix, but are not connected with the 
glauconite grains. Unfortunately there are no Stromatopore in 
these beds, otherwise we might have an almost precise recurrence 
of the relations of serpentine with Hozoon in the Laurentian*. 
Another appearance which may be mentioned in this connexion 
occurs in certain beds of Utica Slate in the vicinity of the trappean 
mass of Montarville, and converted into a hard sonorous rock. In 
one of these are stems of crinoids which have retained their external 
form, while the calcareous material has been entirely removed and 
replaced by a soft green crystalline mineral whose physical and mi- 
croscopical characters are those of chlorite, and which in any case 
may be regarded as one of those hydrous silicates sometimes termed 
“ viridite.”’ 
3. Limestone of Pole Hill, New Brunswick, and of Llangwyllog in 
Anglesey—tIn a paper in the Transactions of the Royal Irish 
Academy, and subsequently in ‘ Life’s Dawn on the Earth,’ I noticed 
a remarkable limestone discovered by Mr. C. Robb, of the Geological 
Survey, at Pole Hill in New Brunswick, and believed to be of Upper 
Silurian age. It is composed of fragments of crinoids and shells, 
the cavities of which are finely injected with a hydrous silicate of 
alumina, iron, and magnesia, the composition of which, according to 
Dr. Hunt, approaches to that of the pollyte of Von Kobell, and also 
to that of a hydrous silicate described by Hoffmann as filling the 
cavities of specimens of Hozoon found in Bohemia. It has also some 
resemblance to the loganite which mineralizes the Hozoon of Burgess, 
in Canada. At the same time I mentioned a specimen of limestone 
of similar character which I had found in the McGill-College collec- 
tion, and which I supposed to be from Wales. It is labelled “ Llan- 
golloc,” and belonged to the collection of the late Dr. Holmes, of 
Montreal. Professor Ramsay, to whom I have applied for informa- 
tion as to the locality, kindly informs me that the name is probably 
“‘ Llangwyllog,” that the place so named is in Anglesey, and that 
limestone of Lower Silurian or Cambrian age occurs in its vicinity. 
A portion of this specimen was submitted to Dr. Sterry Hunt, 
from whose analysis it appears to be of similar character with that 
of Pole Hill, and like it injects in the most beautiful manner the 
pores and cavities of crinoids, shells, and coralst. The limestone 
containing this silicate is of subcrystalline texture, with occasional 
bright cleayage-faces which belong to crinoidal fragments. Its 
colour, owing to the included silicate, is dull olive, and it shows oc- 
casional small deep green and reddish specks. Its aspect is so waxy, 
that at a little distance it might be mistaken for an impure ser- 
pentine. 
When examined with the microscope, the flocculent olive-green 
silicate is seen to penetrate the mass exactly in the manner of the 
* Report of Geological Survey of Canada, 1866. 
t As the analyses of these specimens by Dr. Hunt have not been published 
