



22 
of this part from its earliest and youngest form, when it possessed a width and 
elevation not exceeding one-fourth of a line, to its mature growth, and the size of 
some inches. The very minute bases above mentioned,* adhere to a superior 
columnar joint (T. 11. fig. 1.) and possess in the centre a very minute column sur- 
rounded by laminz which form a small regular cone. ‘These, in combination 
with numerous other specimens in different stages of growth, and with their lon- 
gitudinal sections, prove that the exuded calcareous matter forming the pedicle 
or base, became completely indurated soon after its deposition, since the 
lowest columnar joints to be traced at the bottom of the base are very minute, 
(Pu. ıı. fig. 3. and 4.) not exceeding the proportions of the youngest specimens, 
(and must therefore have been prevented from increasing and expanding in their 
growth by the unyielding nature of materials surrounding them) whilst the ` 
‘succeeding joints become in series at certain intervals of four, five, or even . 
more, successively larger and larger. It may also be seen that the inferior 
portions of the alimentary canal enveloped in the base, become gradually filled 
up and obliterated, being no longer required in this part of the animal (T. ır. 
fig. 4. and 10.) where all increase had long ceased. 
The secretions of the indurating calcareous matter took place in consider- 
able quantity when the animal grew up, and appears to have flowed abundantly 
from vessels between the radiating surface of two joints. Thisis beautifull y dis- 
played in sections of large bases (T. rz. fig. 10.) where the differently coloured 
laminae demonstrate the gradual formation of this part, their lines and the man- 
ner in which they spread over and encompass extraneous matter which happened 
to be in their way, proving the original fluidity, or rather viscidity of the mass. 
These lines prove also decidedly that the irregular conical mass of the base 
is made up of distinct laminz, concentric and parallel to the outer surface of the 
cone, placed one within the other, and resulting from successive or periodical 
Increase by deposition. In longitudinal sections, as we have already stated, 
these lines are decidedly seen, but lines of separation are also seen traversing 
* These very minute bases are interesting, as affording a proof that the propagation of these 
animals must have been oviparous; since from their size they must have belonged to the very 
earliest and almost embryotic state of the animal ; and yet are found affixed, not to the parent’ 
but to adead plate; whereas the offspring produced by gemmiferous generation, 
&ached from the parent's body till it has obtained a considerable size, 
8 body, 
never becomes de- 

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