CHAPTER OF CRITICISM. 
215 
thing of my own^—that is another affair; if I am enabled to please^f, as you are 
kind enough to think I do, I am satisfied. You do wisely in reporting the Trans¬ 
actions of the London societies; it will be advantageous in many ways. The 
Chapter of Miscellanies ” is another department that I trust, and am indeed 
sure, you will find it your interest to keep up. 
Yours, very sincerely, 
Edwin L]^es« 
CHAPTER OF CRITICISM. 
Some Observations on Ananchites and Spatangus. 
To the Editor of the Naturalist 
London, Ma^ 17, 1837. 
Sir, —In the last number of The Naturalist 101), I observe a slight error 
occurring in an extract from Karsten’s Archiv. fur Mineralogie, relating to the 
singular appearance sometimes presented by the casts of Echinites, owing to the 
existence of crystals of calcareous spar upon the interior of the original shell. 
The translator has made use of the word blade instead of plate, by which latter 
term the polygonal portions composing the external skeleton of the Echinus are 
designated. The phenomenon referred to in the work above quoted, and which 
the writer has explained by the examination of two fossils in the Royal 
3\Iineralogical Museum of Berlin, is an extremely puzzling one to those who may 
meet with a ‘‘ Honey-comb Echinus,” and are ignorant of the mould upon 
which the cells are formed. I am not aware that any solution of the problem has 
been published elsewhere, although the phenomenon itself, and the manner in 
which it has been produced, must be familiar to those who have made this 
interesting class of fossil bodies an object of investigation. 
Fossil Echinites having crystals of carbonate of lime deposited upon their 
internal surface, although by no means of common occurrence, are found in all 
chalk districts which furnish the remains of Uadiata in abundance. I have 
never seen these crystals lining the entire surface; about half or a third only 
being thus occupied, and usually confined to the spherical portion of the shell. 
It is a curious fact also, that (so far as my own observation has gone) this 
peculiarity is only exhibited by the genera Spatangus and Ananchytes. 
* The papers of our valued correspondent are always sure not only to be interesting to all ' 
classes of readers, but also to contain panch original information to attract the attention of the 
scientific naturalist.—En. 
