50 Mr. J. Brtce on Coal Bearing Strata in the Island of Bute. 



able seams have been searched for, but as yet without success. It is 

 probable, indeed, that from the position of these beds and their limited 



(o) Limestone ; (6) shak with thin coal seams; (c) limestone breccia ; QT) trap. 

 extent inland, they will, like the similar strata in Arran, never turn out 

 to be of much economic value. Their occurrence here, however, is a 

 matter of Teat geological interest, as presenting a striking analogy with 

 An-an, mui-king, with it, the extreme outer limit of om' great coal field, 

 and attesting the uniformity of the conditions of the surface which pre- 

 vailed at this remote era. 



The fossils by which the strata were identified are given in the follow- 

 ing Hst. The species have been determined by Mr. Fraser, from 

 specimens in liis collection and my own. To his well known skill in 

 this department I wilhngly submit my own judgment. 



Plantct. 

 Sphenopteris bifida, not uncommon in the shales. 

 affinis, ditto. 



furcata, ditto. 



dilatata, rare. 



Pecopteris nervosa, rare. 



Calamites nodosus, abundant in the shale and sandstones. 



undulatus, ditto. 



Trigonocarpum ohvseforme, rare. 



Brachiopoda. 



Producta punctata, not abundant. 



■ sulcata, ditto. 



Spirifer semicircularis, somewhat common. 



trigonalis, rare. 



dupHcostata, rare. 



Lingula squamiformis, abundant in the shales. 

 Orthis radialis, rare. 



