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of hardness, forming in some places a white free-stone, and in others 
a softer fire-stone. This stratum affords striking instances of the fact, 
first noticed by Mr. Smith, of certain organic remains being peculiar 
to, and only found lodged in, particular strata. The chief fossils 
which are found in this stratum are ammonites of a tolerably large size ; 
and a smaller species of an oval form, different from those found in 
any other strata, Yol. III. PL IX. Fig. 6. Having obtained a specimen 
of this species from Steyning in Sussex, and knowing that the stratum 
of hard chalk was worked near Heytesbury in Wiltshire, I wrote to 
my late respected friend, Mr. Cunnington, to inquire if these fossils 
were found there or not ; and I was agreeably surprised at receiving 
of him, from that stratum, an oval ammonite of the same species with 
that which I had found at Steyning. In this stratum are also found 
the remains oi scaphitce, Vol. III. PI. X. Fig. 10*. 
Immediately on this stratum is placed that of the soft chalk, con- 
taining silex in the state of sand with interposed layers, and large 
interspersed, and irregular nodules of black flint. The fossils of this 
stratum differ in a very remarkable degree from those of all the 
inferior strata. Here are, I believe, never found ammonites, trigo- 
nitoe, or scaphitce, which were found in the preceding stratum. The 
fossil remains which are here found are of echinatce of different species, 
particularly of cidaris, galea, galeola and spatangus ; here are also 
found stellitce, terehratulitce, serpulitoe, ostreitce, belemitce, a thorny 
pectenites, turbinated and other madreporitee. The remarkable limpet- 
like shell, p. 51, PI. Y. Fig. 3. of the present volume, which is seen 
I believe in no other stratum ; teeth, and rarely the scales and hones of 
* The specimen, PI. XVIII. Fig. 4, is very interesting from its showing the peculiar nature 
of the fossils of this stratum. It was found in the upper part of the Sussex hard chalk. It has 
very much the appearance of an echinital spine ; but the smaller end is split into several rugae : 
and In another specimen, not in other respects so perfect, it is seen, that this rugous termination 
was an organ of attachment, the fossil being thereby attached to a piece of shell. On this ac- 
count, there appears to be reason for supposing it to be part of a shell of the same genus with 
the fossil represented PI. VII. Fig. 18, of this volume. 
