GIBB — ON CANADIAN CAVERNS. 



179 



footing, and wlien in the cave a person can stand upright, with 

 plenty of room to spare. The roof is composed of limestone, and 

 lined with a coating of stalactitical carbonate of lime, but from which 

 there do not project any stalactites ; some portions of the floor, how- 

 ever, contain stalagmites, a few specimens of which were collected. 

 No bones of animals were found, possibly owing to the presence of 

 the water. Their existence can only be ascertained by pumping the 

 water out, which may overlie a sort of breccia. The ridge, which is 

 composed of the Trenton limestone, here partakes somewhat of the 

 character of a hill, at the base of which is an opening leading into 

 the interior of the cavern. It was accidentally discovered some 

 thirty years ago on the occasion of a party of hahitans going out 

 huntiijg. The dog belonging to the party commenced to scratch at 

 the spot which forms the entrance, and suddenly disappeared ; the 

 animal had fallen into it, and his cries brought the hunters to the 

 hole in the ground. The opening was enlarged, and the party 

 entered by crawling on their hands and feet. 



From the description of the cavern, it would appear that its origin 

 is due to upheaval from below, producing a dislocation of the stratum 

 of limestone and the formation of a wide fissure, which may be found 

 ultimately to extend much farther than the distance given in the 

 foregoing account. The discovery of this cavern was looked upon 

 at the time as something very wonderful. 



(To be continued.) 



THE CARBONIFEROUS SYSTEM IN SCOTLAND CHARAC- 

 TERIZED BY ITS BRACHIOPODA. 



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

 the Greological Society of Glasgow, etc., etc. 



( Continued from Vol. iu., p. 11 5. J 



XXXVI. — ^PuoDUCTUS cosTATUS. Sow. PI. 11, figs. 23-24; pi. iv., fig, 25. 



Producta costata. J. de C. Sowerby, Mineral Conchology, vol. vi., p. 115j 

 pi. dlx., fig. 1, 1827. 



This species appears to vary somewhat in appearance, but is usually trans- 

 versely semi-cylindrical, the hinge-line being at the same time the widest 

 portion of the shell. The ventral valve is very much vaulted, and usually 

 longitudinally divided by a median depression or sinns of variable depth. The 

 beak is small, and does not overlie the hinge-line, while the ears are of moderate 

 dimensions and clearly defined. Exteriorly the surface is ornamented with 

 numerous longitudinal ribs, wliich increase in number by means of occasional 

 intercalations ; certain ribs will also disappear before having attained the 



