DAVIDSON — SCOTTISH CAEBONIFEROUS BEACHIOPODA. 219 



and two of tlie Chazy limestone species.* The fossils are very 

 numerous at the month of the cavern and large flat exposure of strata 

 above the bridge close by. 



It is a soui'ce 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. 

 From other somxes I learn the cavern is not only extensive, but likely 

 to branch ofi" in several directions. 



30. — Probable Caverns in Iron Islands, Lake I^'ipissing. 



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 frequently 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 inter stratified 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 be continued.) 



THE amBONIFEROUS SYSTEM IK SCOTLAJSTD CHARAC- 

 TERIZED BY ITS BBACHIOPODA. 



By Thomas Davidson, Esq., F.B.S., F.G-.S., Hon. Member of 

 the Geological Society of Glasgow, etc., etc. 



( Continued from page 184.^ 



XLII. — Chonetes Hardeensis. PhiUips. PI. ii., figs. 2-7. 



OrtUs Eardrensis. Phillips' Figures and Descriptions of the Palaeozoic Fossils 

 of Cornwall and West Somerset, p. 138, pi. Ix., fig. 104, 1841. 



The shells composing this species vary but slightl;^ m shape, being marginally 

 semicircular, concavo-convex, and about one-third wider than long. The hinge- 

 line is straight, and either a httle shorter, with its cardinal angles rounded, or 



* Geol. Survey of Canada. Eeport for 1855. 

 t Geol. Survey of Canada. Report for 1857, p. 154. 



