On Rachiopteris Williamsoni sp. nov., a New 
Fern from the Coal-Measures. 
BY 
A. C. SEWARD, M.A., F.G.S., 
University Lecturer in Botany, Cambridge. 
With Plate XIII. 
I N 1876 1 Professor Williamson published an account of the 
extremely interesting genus Myeloxylun , Brongniart (Sten- 
zelia , Goeppert, Myelopteris , Renault), a plant chiefly known 
from fragments of petioles which have been obtained from the 
English Coal-measures, the famous silicified deposits of Autun, 
and other places. The present paper deals with one of 
Williamson’s specimens, of which Figs. 7 and 8, PL II, and 
Fig. 17, PL IV, of the Memoir referred to, represent transverse 
and longitudinal sections. 
Having obtained access to the specimens of Coal-measure 
plants in the collection 2 of the late Mr. Binney, I found some 
unusually well-preserved sections of Myeloxylon , and published 
a brief description of them in the Annals OF BOTANY for 
1:893 3 . In the same paper there were included some notes of 
various other examples of the same genus, including a few 
sections which Professor Williamson had generously placed at 
my disposal for examination. Among the latter I found that 
in some sections there were certain characters which led me 
to separate them from Myeloxylon , and to place them in the 
convenient genus Rachiopteris , as a new species, R. Wil- 
1 Phil. Trans., Vol. clxvi. 1876, pt. i. p. 1. 
2 In the Wood wardian Museum, Cambridge. 
3 On the genus Myeloxylon (Prong.) : Ann. Bot, Vol. vii. 1893, p. 1. 
[Annals of Botany, Vol. VIII. No. XXX. June, 1894.] 
