[ 459 J 
XI. On the Organization of the Fossil Plants of the Coal-Measures .— Part XII. 
By W. C. Williamson, LL.D., F.R.S., Professor of Botany in the 
Victoria University, Manchester. 
Received May 4,—Read May 11, 1882. 
[Plates 27—34.J 
In Part IX. of this series of memoirs (Phil. Trans., Part II., 1878, pp. 319-322) I 
described, under the generic name of Astromyelon, a series of stems, transverse 
sections of which might readily be, and for some time were, mistaken for sections of 
Calamites; but I pointed out the differences which separate widely these two types 
of stem. Attention was directed to the almost universally decorticated condition in 
which the Astromyelons were found; the only exceptions being one or two examples 
(loc. cit., Plate 19, fig. 7, d), in which the vascular zone was surrounded by a thin 
cellular layer. 
At the recent meeting of the British Association at York, Mr. Cash, of Halifax, 
and Mr. Hick, of Harrogate, described a remarkable stem, discovered by Mr. Binns 
in the Halifax beds, and to which they gave the name of Myrioiohylloides William- 
sonisA I shortly afterwards suggested the desirableness of substituting the generic 
name of Fhelophyton as preferable to that of Myriophylloides, for reasons given in the 
note in which this suggestion was made.t 
I subsequently received a letter from Mr. Spencer, of Halifax, telling me that he 
had obtained additional specimens of the new plant, which convinced him that it was 
a corticated state of the Oldham Astromyelon which I had previously described. All 
the specimens discovered up to the present time having been placed in my hands by 
my excellent auxiliaries, and undergone a careful investigation, I have no doubt about 
the correctness of Mr. Spencer’s conclusion. 
The plant proves to be a much more varied and remarkable one than I had previously 
thought. 
The simplest form in which it has hitherto been met with is represented in fig. 1. 
This specimen, which is black and carbonised, is a transverse section of an axis which 
differs very widely from the ordinary forms of the Oldham Astromyelon. In its centre, 
* This interesting communication has since been published in the Proceedings of the Yorkshire Geological 
and Polytechnic Society, vol. vii., part iv., p. 400, 1881. 
t ‘Nature,’ Dec. 8, 1881, p. 124. 
