174 Dr Hibbert on the Limestone of Burdiehouse 



minous shale, where it appeared as a sort of harbinger to the 

 rich primeval flora, which was doomed to follow. And in other 

 sites, namely in Linlithgowshire and Ayrshire, the Sphenopteris 

 affinis equally shewed itself as one of the first created plants 

 of the carboniferous epoch. 



Much rarer ferns, which in the limestone of Burdiehouse ap- 

 pear associated with this very ancient plant of the coal-fields of 

 Scotland, are the Sphenopteris bifida, the Sphenopteris linearis, 

 and some few others. 



The Sphenopteris bifida exhibits a greater delicacy in the 

 divisions of its pinnulae than a fern which it greatly resem- 

 bles from a different locality, the Sphenopteris dissecta of M. 

 Adolphe Brongniart, to which the French botanist has as- 

 signed the highest antiquity among the carboniferous group of 

 rocks. Yet there is still so much affinity between the two, that 

 they might be readily confounded one with another. The fern 

 of Burdiehouse, however, may be referred to a bipinnated plant 

 which Messrs Lindley and Hutton have distinguished by the 

 name of Sphenopteris bifida. (See Fossil Flora, plate 53.) It 

 is placed by these authors in the vicinity of Sphenopteris myrio- 

 phylla, from which it is known by its leaves not having more 

 than three or four primary divisions, and these not radiating from 

 a common centre, and repeatedly dichotomous, but arising from 

 a flexuose axis, and simply bifid. The difference between the 

 Sphenopteris bifida and that of dissecta, as Professor Lindley 

 has obligingly remarked to me, is, that the Sphenopteris bifida is 

 a smaller plant with much more slender divisions, and with the 

 principal pinnae longer and more repeatedly divided. 



The third Sphenopteris resembles one which has been hitherto 

 only found at Oldham in Lancashire, having been procured by 

 myself from a deep-seated bed belonging to the great coal-field of 

 Lancashire. A specimen was many years ago placed in the hands 

 of M. Adolphe Brongniart, who, in describing it under the 

 name of the Sphenopteris linearis, has thus defined it : " S. foliis 



