174 Dr Hissert 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 pinnule than a fern which it greatly resem- 
bles from a different locality, the Sphenopteris dissecta of M. 
Avotrue Broneniart, 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 Linpiry 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 Linpiey 
has obligingly remarked to me, is, that the Sphenopteris bifida is 
a smaller plant with much more slender divisions, and with the 
principal pinne 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. Anotrne Bronenrart, who, in describing it under the 
name of the Sphenopteris linearis, has thus defined it: “ S. foliis 
5 
