67 
chalk that may not be occasionally met with imbedded in flint. I 
have seen the bones of Saurians and Echinoderms ; I have in my own 
collection both palatal and sharp maxillary teeth of more than six spe- 
cies of fish ; the common Ananchytes and Spatangus, which have their 
interior filled with flint, are good examples of its extreme fluidity. 
Thin portions, which can with a little management be broken from 
flints, form good objects for the microscope: some of these contain 
Foraminifera and Infusoria in great abundance, the scales of fish, and 
many organic forms, which have not been particularly noticed. 
On entering a pit of upper chalk, the stranger is surprised at seeing 
detached, but usually horizontal rows of flints distributed through 
the mass, varying from three to six feet apart, in regular divisions ; 
these are the remains of the heavier zoophytes, which have attracted 
the silica and sunk to the bottom of the pulpy fluid; and, as Dr. Buck- 
land observes, each division may indicate a period so long as to con- 
solidate the preceding layer*. In some localities (though rarely) the 
flint strata assume a vertical position, running in thin seams from one 
to two inches in thickness; this is well seen in the section of the 
chalk at Findon Hill near Worthing. 
Among the spongeous bodies which are abundant in the upper 
chalk, there is one that claims our peculiar attention—the Choanites 
Konigit of Mantell. I have given a drawing of this sponge, as near as 
possible to its original form: it is found in great abundance on the 
beach of those shores which are in approximation to the Chalk for- 
mation, and of late years has been much sought after under the name 
of pebbles or agates. This sponge is often more or less converted 
into calcedony, yet still in many instances preserving its structure, and 
* Most of the chalk, and many recent sponges, contain needles or spicula of flint, and some 
zoophytes and many marine plants have the power of secreting siliceous matter. The boiling 
springs of the Geyser in Iceland contain also much silica in solution. It occurs also in the 
waters of Carlsbad and Bath. 
K 2 
