DAVIDSON — SCOTTISH CARBONIFEROUS BRACHIOPODA. 219 
and two of tlie Chazy limestone species.* The fossils are very- 
numerous at the moutli of the cavern and large flat exposui-e of strata 
above the bridge close by. 
It is a source of considerable regret to me that a more extended 
account of this very interesting cavern has not been given, with a 
description of its interior, and where and how the stream disappears. 
Prom other sources I learn the cavern is not only extensive, but likely 
to branch ofi" in several dii'ections. 
30. — Probable Caverns in Iron Islands, Lake Nipissing. 
Iron Island lays about midway between Duke's Point, one of the 
Indian settlements at the western extremity of the Great North Bay, 
and the French River, in Lake Nipissing, recently explored by Mr. 
Murray. It is composed principally of the Laurentian rocks ; here 
and there, however, the crystalline limestones of this formation crop 
out, being frequently associated with iron ore. The beach near the 
outcrop is strewed with masses of all sizes, from great boulders 
weighing several hundred pounds to small rounded pebbles not 
larger than marbles. The limestone thus associated with the iron- 
ore is fi'equently cavernous, and the numerous crevices and smaller 
fissures are thickly lined with crystals of blue fluor-spar and red 
sulphate of barytes, or cockscomb-spar. As the cavernous crystalline 
limestones are here interstratified with, and cut across by, trap, often 
assuming the concretionary character, it is probable some day that 
caverns may be discovered in the elevated cliffs of the island.f 
(To he continued.) 
THE CiLRBONIFEROUS SYSTEM IN SCOTLAND CHARAC- 
TERIZED BY ITS BRACHIOPODA. 
By Thomas Davidson, Esq., P.R.S., P.G.S., Hon. Member of 
the Geological Society of Glasgow, etc., etc. 
( Continued from, page 181.^ 
XLII. — Chonetes Hakdrensis. Phillips. PI. ii., figs. 2-7. 
Orthis Hardrensis. Phillips' Pigures and Descriptions of the Palaeozoic Possils 
of Cornwall and West Somerset, p. 138, pi. Ix., fig. 104, 1841. 
The shells composing this species vary but shghtly in shape, being marmnaUy 
semicircular, concavo-convex, and about one-tliii'd wider than long. The liinge- 
liae is straight, and either a Httle shorter, with its cardiaal angles roimded, or 
* Geol. Survey of Canada. Eeport for 1855. 
t Geol. Survey of Canada. Report for 1857, p. 154. 
