SPENCER : ASTROMYELON. 
443 
have named — Amyelon radiatus — most probably belongs to the 
former while the other is more allied to the latter group. 
It has already been pointed out that the woody cylinder of 
Astromyelon bears a resemblance to that of Calamites. I wish 
now to draw attention to the woody cylinder of Asterophyllites. 
It was regarded by some authorities as the leaves and young 
branches of Calamites, along with Sphenophyllum and Annularia ; 
but the discovery of its steins in a good state of preservation has 
shewn that Asterophyllites is an independent plant. In the 
French coal fields Sphenopyllum has also been found preserved in 
a similar way, and its structure closely resembles that of Astero- 
phyllites ; but hitherto neither Sphenophyllum nor Annularia have 
been recognized in sections from the coal-balls. 
Transverse sections of Calamites and Asterophyllites shew 
how widely they differ from each other : in Calamites the woody 
cylinder is formed of an indefinite number of wedge shaped masses, 
varying from eleven to sixty, according to the size of the stem, 
whereas in Asterophyllites there are always three large wedges 
in the young and old alike. 
Again, the pith in Calamites is confined^to a narrow zone 
surrounding the woody wedges, the centre of the plant being hol- 
low, as it is in the modern horse tails, whereas, the centre of the 
stem in Asterophyllites is occupied by a remarkably characteristic 
pith, triangular in section and composed of vascular tissues ; from 
each of these three angles extends a woody wedge, which in very 
young stems are small in size, and the spaces between them filled 
with parenchymatous tissues, but in older forms they increase in 
size until they form a solid cylinder. In all other respects the 
character of the wedges is the same as those of Calamites and 
Astromyelon. The structure of the bark which is generally pre- 
served is also different from either that of Calamites or Astrom- 
yelon. 
From this brief ascount of Astromyelon and its allies, it will 
be seen that in one of the most important structures — the ligneous 
