1849.] 



BROWN ON ERECT SIGILLARI^. 



355 



I have now the satisfaction of forwarding sketches and descriptions 



of two curious fossils from the roof of the main coal, calculated in my 



opinion to afford some interesting information concerning the habit 



and mode of growth of Sigillaria alternans ; and at the same time 



to clear up all doubts respecting the true nature of the " dome-shaped 



fossil," figured and described in Lindley and Button's ' Fossil Flora,' 



vol. ii. pref. p. xiii. 



Fig. 1. 



c, 



stump of Sigillaria alternans, one-twelfth of the natural size. 



Fig. 1 is a sketch of an upright stump, sixteen inches in height 

 and twelve inches in diameter at the top, which dropped from the 

 roof of the seam some time after the coal had been removed ; the 

 greater part of the branching roots had fallen do^vn and been stowed 

 aw^ay amongst the rubbish of the mine before the stem was discovered ; 

 the few that remained are in external appearance true Stigmarise, but 

 being filled up with soft shale, no traces of internal organization can 

 be observed, except occasionally a flattened central core. The upper 

 part of the stem was covered with a coaly bark one-fifth of an inch 

 in thickness, which was closely marked with irregular short striae in 

 a vertical direction, and by long projecting wrinkles running spirally 

 round the stem as shown at c (fig. 1). A thin layer of hard shale 

 which envelopes the bark, completely conceals the leaf- scars. Lower 

 down the bark was thinner and very smooth, whilst that which 

 covered the roots a, h was so exceedingly thin and friable, that it 

 fell off on the slightest touch. 



The leaf-scars on the decorticated stem are very sharp and distinct ; 

 they begin close to the ramifications of the roots, and run in single 

 spiral lines over a zone three or four inches in width ; above this zone, 



