CLARK : GLACIAL SECTIONS. 
439 
general dead level are of glacial origin ; whilst the river flood and 
tidal deposits have largely obliterated these undulations by filling 
them up, perhaps as much as 50 feet above the level to which the 
river first cut down its bed in the opening of the post-glacial 
epoch. 
EXPLANATION OF PLATE XXIII., FIG. 1. 
SUPERFICIAL DEPOSITS POUND YORK. 
Laid down on the one inch map of the Ordnance Survey from notes 
and plans. 
A. New Goods Station. 
B. New Passenger Station. 
C. St. Paul's Square. 
D. Campleshon Pond. 
E. Holdgate Nurseries. 
F. Cuttings on Foss Islands Railway. 
G. Friends' Retreat. 
ASTROMYELON AND ITS AFFINITIES. BY JAS. SPENCER. 
This new genus of fossil plants was first described and introduced 
to the scientific world so recently as the year 1878, by Professor 
W. C. Williamson, F.R.S., in his ninth memoir " On the Organiza- 
tion of the Fossil Plants of the Coal Measures." Fragments of 
Astromyelon, however had been previously found and described 
as Calamitean, on account of their close resemblance to similar 
structures in Calamites, both by Mr. Binney and Professor 
Williamson. Since the publication of the above memoir, our 
knowledge of this interesting genus has been largely increased by 
the discovery of a large series of additional specimens by myself 
and other workers in this branch of science. I purpose in this 
paper to give a short sketch of what is known about Astromyelon 
and also of its nearest relations. 
The Astromyelons have been named and described solely 
from the microscopical examination of specimens obtained from 
