INTRODUCTION. 23 
tree, Volute, Natice and Turritelle. The shells were so 
friable as almost to fall into powder on the touch, and pre- 
sented no characters whereby to make specific distinctions. 
With this slight knowledge of the stratum, it is not with- 
out some hesitation that I refer it to the Tertiary Forma- 
tion. Future investigation may prove it to be of older 
origin, when its fossils shall be obtained in a more perfect 
state. 
** No. 2 is a specimen of the rock lying on the above 
stratum, No. 1, and is about the thickness of two feet.” 
This specimen, nearly of the size of the last, consists, 
chiefly, of a single and imperfect valve of alarge Ostrea. It 
appears to be a compact calcareous rock, with numerous 
grains of dark green sand; and besides the Ostrea men- 
tioned above, Flustre, and a Teredo may be observed in 
it. On examination, the matrix proved to have nearly 
thirty-two per cent of carbonate of lime. This bed may 
be referred to the same Formation with the last. 
“No. 3. This is the stratum from which are taken the 
specimens of organic remains in the box. _ It is just seven- 
teen feet thick. This specimen* is a fair representation of 
the whole stratum.” 
It is in this stratum that the fossils described in this 
memoir are found. It is exceedingly rich, and some idea 
may be formed of the vast number of new species contain- 
ed in it, when it is recollected that I have received from 
Judge Tait, at four or five different times, more than two 
hundred and fifty species. Were I to conclude from the 
examination of what were received, I would say that this 
is a very small portion of what will be found in that 
stratum. 
The bed is composed of loose quartzose, brownish sand, 
the grains of which are small and angular. The most 
delicate specimens are, therefore, with a little caution, 
* A very large Crassatella, since described by Mr Conrad as C. alta. 
