60 
impregnation with silex, were simultaneous or took place at very remote 
periods, can perhaps only be determined by future observations : 
the fact is, however, indisputable, the original matter, of which the 
fabric of the animal was composed, has been removed, and its place 
supplied by silicious matter deposited from its solution in some appro- 
priate menstruum. 
For the farther illustration of this interesting fossil, I have caused 
various sections of it to be made, to admit of an examination of its parts 
in different positions and directions. By a longitudinal section, much 
of the real disposition of the plates composing the star is displayed, 
the continued perpendicular plates may be distinctly traced, the absence 
of any transverse septa may be ascertained, and that plumose appearance, 
which has sometimes procured for this fossil the appellation of feather- 
stone, may be plainly seen. 
In Plate VIII. Fig. 39} of BourgueFs Traite des Petrifications, is a 
very close representation of the characteristic forms which this fossil 
assumes ; although the figure is in other respects highly defective. 
In the description of the plates, which is throughout lamentably 
meagre, we only meet with champignon koile as the illustrative desig- 
nation of the representation of this curious fossil. 
This fossil is exceedingly common in the northern parts of Wiltshire ; 
being turned up very frequently in the ploughed lands. 
Dr. Woodward evidently refers to this particular corallite under the 
head of Coralloidea columnaria penta'Mra ; and specifies it as Coralloidea 
oblonga pentdedra laminis d superjicie ad axem tendentibus. He de- 
scribes a specimen, which he obtained from Wiltshire, as “ A grey 
semi-pellucid flint, the ground much like the Indian agate, but thick 
set with white pentagonal columns, about a quarter of an inch in diameter. 
They are made up of several longitudinal thin plates, all set edgeways 
towards the axis. The columns stand parallel to one another : and 
are placed at equal distances, being about one-twentieth of an inch 
