216 
CHAPTER OF CRITICISM. 
Each crystal invariably occupies a separate plate, its base never extending 
over a suture. They are consequently disposed in rows, the size of each crystal 
diminishing from the base towards the apex of the Echinus. Now, wherever 
the chalk formation contains flint nodules in any considerable quantity, a certain 
proportion of the Echini have their cavities filled with silex, and if by natural 
or artificial means the shell (which is not itself silicified) be removed, we obtain 
a very accurate cast of the interior. These siliceous casts are generally 
abundant wherever the chalk has been abraded by currents of water, the im¬ 
bedded flints being left in the form of superficial gravel. It is obvious 
that a deposition of calcareous crystals, in the cavity of an Echinus, would be 
no obstacle to a subsequent infiltration of silex, but a cast formed under these 
circumstances, instead of presenting elevations, corresponding to the sutures and 
ambulacral perforations of the shell, would exhibit the impression of these 
crystals. The history, therefore, of the Honey-comb Echinites is readily under¬ 
stood, but the existence of the crystals is, perhaps, deserving of some further 
consideration. 
The writer in the Archiv mentions, that in one specimen the crystals were 
outside the shell. I have never known an instance of this nature, and I do not 
consider it possible for the exterior surface of the Echinus to regulate the size 
and disposition of the crystals in the same manner as the interior. 
Perhaps the above brief notice may to some of your readers place the matter 
in a clearer light than the passage of which you have given a translation. 
Your obedient servant, 
Edward Charlesworth. 
Neville Wood, Esq. 
On the Discovery of Cinclidium stygium in Britain. 
To the Editor of the Naturalist. 
—I have this moment seen, for the first time, the number of The Naturalist 
for May, and am not a little surprised to find myself mentioned in it (p. 101) 
as having presented to the Botanical Society of London a new plant found on a 
Moor near “ Malkham Farm” Yorkshire, and named by me Cinclidium styrzi- 
cum. Now it is quite true that I did, some time ago, communicate to the 
Society, through the medium of the Curator, Mr. Daniel Cooper, a specimen 
or two of a Moss new to Britain, but it was neither discovered nor named by me. 
It is the Cinclidium stygium, and has long been known as a native of the North 
of Europe. I believe it was first described by Swartz in Diario Schrczderi, 
and subsequently by Wahlenberg in Flora Lapponica, p. 355; it is also 
figured in the Flora Danica, tab. 1422. 
This very interesting addition to the British Flora was. discovered on the 
