446 : NATURAL HISTORY MISCELLANY. 
plates of crinoids, cemented with a little calcareous spar. The 
crinoidal remains were, however, found to have their pores filled 
with a peculiar silicate, which is exposed in relief when the sur- 
face of the limestone is attacked by an acid, and then appears as- 
a congeries of small cylindrical rods or bars, anastomozing and 
forming a beautiful net-work, which, under a magnifying glass, ex- 
hibits a frosted crystalline surface, and resembles the variety of 
arragonite known as flos ferri. This silicate, which also fills small 
interstices among the other calcareous fragments making up the 
limestone, is greenish in color and forms about five per cent of the 
_ rock. Though insoluble in dilute acids, it is completely decom- 
posed by strong acids, and is found to be a hydrous silicate of 
ferrous oxide and alumina, with some magnesia and a little alkali, 
closely allied to fahlunite and to jollyte. The results of its analy- 
sis appear in “ Silliman’s Journal” for May. 
Dr. Hunt remarked that this process of infiltration, by which 
the minute structure of these Palæozoic crinoids has been pre- 
served, was precisely similar to that seen in the glauconite casts 
of more modern foraminifera, and in the Eozoon of older times. 
This ancient caleareous rhizopod, though most frequently preserved 
by serpentine, had been shown by himself in Canada and by Hoff- 
man in Bohemia, to be in some cases injected by silicates related 
in composition to that of these crinoids. He then proceeded to 
speak of the great class of silicates of which serpentine, loganite, 
pyrosclerite, fahlunise, and jollyte are members, and which are 
generally described as the results of pseudomorphic changes of 
preéxisting silicates or carbonates, but which he, since 1853, has 
maintained to be original aqueous depositions, similar in their ori- 
gin to the related mineral glauconite; a view now adopted by 
such investigators as Naumann, Scheerer, Gumbel and Credner. 
He noted in this connection the bearing of these facts on the Eo- 
zoon Canadense of Dawson, the organic nature of which, though 
almost universally admitted by zoologists and mineralogists, WaS 
nevertheless still questioned by Messrs. King and Rowney. These 
gentlemen object that the ancient rocks in which Eozoon is found 
are what are called metamorphic strata, which have been, accord- 
ing to them, subjected to pseudomorphic changes, and therefore, the 
Eozoon may be the result of some unexplained plastic force, whic 
has fashioned the serpentine and other mineral silicates into forms 
so like those of foraminiferal organisms as to deceive the most 
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