376 HICK AND CASH: FOSSIL FLOEA OF HALIFAX. 
is imperfectly retained, but the radiating cellular laminge are suffi- 
ciently distinct, terminating in the outer layer of cortical cells."* 
Now we venture to think that the organization of the cortex 
alone is not sufficient to settle the identity of the plants in question. 
Modern botanists are well aware that in cortical structure; such 
recent aquatic forms as Marsilea, Potamogeton, Utricularia, Bippuris^ 
HoUonia, and Myriophyllurn, have the closest resemblance to one 
another, and yet for the most part, they belong to widely separated 
Natural Orders, and some of them to quite different classes. Hence 
it is obvious that although Astromyelon and Myriophyltoides may 
have a very similar cortical structure, it by no means follows that 
thc}^ have close affinities and much less that they are identical. 
Besides this, the axial structure of Astromyelon, which is its 
leading feature, as hitherto known, bears by no means a close 
resemblance to that of Myriophylloides. Amongst the chief charac- 
teristics of the former plant, are " the distinct outline of peculiar 
form of the conspicuous vascular wedges constituting the exogenous 
zone, and the relations of these wedges to the large medulla which 
that zone enclosed."f In Myriophylloides, so far as specimens in 
our possession go, and so far as those described by Prof. Williamson 
show, these characters are altogether absent. 
Further, the specimen of Astromyelon chiefly relied on by Prof. 
Williamson is very imperfect, only a small portion of the cortex" 
being preserved. 
This of itself seems to us sufficient to induce a suspension of 
judgment until better preserved specimens shall show whether the 
cortical plates and air canals had the same arrangement as we 
described in Myriophylloides. 
Whatever may be the case then, in the near or remote future, 
we can scarcely regard the identity of these two plants, as at present 
fully established. The interest taken in them will, however, continue 
to exert a stimulating influence upon all Palceophytologists, so that 
we may fairly anticipate more conclusive evidence at no distant date. 
Apart from the question of affinities, little can be said of Myrio- 
*Loc. cit. p. 460. 
t Williamson's Memoir, part XII., p. 4G0. 
