520 
PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
of very diversified character, but in no one example did I discover the smallest frag¬ 
ment of a Diatom. 
Mr. F. Kitton, of Norwich, informs me that he examined samples of Welsh, 
Durham, and Newcastle coals, as well as others from “ Inland ” collieries, and from 
Scotland. Like myself, he could find no trace of Diatoms. The Rev. E. O’Meara,* 
of Hazlehatch, near Dublin, states that he examined specimens from the Whitehaven 
coal-field. He says in a letter: “ The result was that in all cases not the slightest 
trace of Diatomaceous forms was found; and if any had been present I have no doubt 
they could not have escaped my observation.’' The same correspondent also informs 
me that the Rev. George Davidson, of Logie Coldstone, Aberdeen, a gentleman 
highly competent to conduct such investigations, also examined a series of coals with 
the same negative results. Under these circumstances I can only conclude that Count 
Castracane has been mistaken as to the source of his Diatoms. 
Calcisphoera. 
It only remains for me to examine a group of objects which may have no claim to 
be noticed in this series of memoirs, since it is quite possible that they may ultimately 
prove to be animal and not vegetable forms; but having already inquired into one 
supposed Radiolctrian with the result of relegating it to the vegetable kingdom, it may 
not be undesirable to examine some other carboniferous organisms, for which a Radio- 
larian rank is also claimed. 
Attention has already been directed to these objects by Professor Judd. In the 
discussion that succeeded the reading of a memoir on siliceous sponges by Mr. Sollas, 
before the Geological Society of London, Professor Judd is reported! to have “referred 
to the discovery of Radiolarians in carboniferous rocks near Chester, and stated that, 
on dissolving portions of the rock that show the Radiolarian structure, the latter 
entirely disappears, but at the same time the rock itself furnishes small crystals of 
quartz. This seemed to be confirmatory of Mr. Sollas’s statements ” — i.e., that 
siliceous organisms imbedded in calcareous rocks might have their siliceous elements 
replaced by carbonate of lime. 
I am indebted to Mr. Siddall, of Chester, for specimens of the limestone in ques¬ 
tion, which comes from Rhydymwyn, near Mold, in Flintshire. It is a very fine¬ 
grained limestone of a light brown colour, containing vast numbers of the minute 
objects referred to by Professor Judd. 
It is impossible to obtain these organisms free from their investing matrix, hence 
they can only be examined either in thin sections of the limestone as transparent 
objects, or on polished fiat surfaces as opaque ones. The differences which they exhibit, 
according to the method of viewing them, throw some light upon them morphology. 
* Now unhappily lost to science, May 6th, 1880. 
t ‘ Quarterly Journal of the Geological Society of London,’ May, 1877, p. 835. 
