red colour, where it is not invested with its cortical part, which is of 

 a grey colour, pervaded by a slight tinge of red, is represented Plate 

 IX. Fig. 8. The pedicle, and the opening at the superior part, are 

 here very perfect. Slight traces of lines, passing from the pedicle to 

 the opening, are discoverable on this specimen, and, doubtlessly point 

 out the arrangement of fibres, by which the animal was enabled to 

 draw in and eject the water which supplied it with food. This fossil, 

 I have reason to believe, is English. 



The set of fossils, which I shall next place before you, is, in many 

 respects, extremely interesting. In the general outline of their form, 

 many of them so much resemble the fossils last described, as, at first 

 sight, to lead to the supposition, that they are only varieties of the same 

 species; but on a closer investigation, several circumstances are ob- 

 served, which seem to warrant a contrary opinion. 



The following are the most remarkable circumstances, in which these 

 fossils differ from the former. First, They appear to be almost en- 

 tirely silicious. Secondly, In that part of the fossil, in which an opening 

 existed in the former species, a rather prominent substance is found. 

 Thirdly, Instead of the finely granulated surface possessed by the 

 former, which appears to have been produced by innumerable minute 

 openings, passing into the substance, the surface is, in the latter, such 

 as might be expected to result from the instillation of lapidifying mat- 

 ter, into a substance of spongeous texture, embraced by numerous 

 ramifying filaments. Fourthly, An entire difference in their internal 

 organization. 



One of these fossils is represented, Plate IX. Fig. 12, with its lon- 

 gitudinal section, displaying its internal organization. The general 

 figure of this fossil approaches very nearly to that of the fossil last 

 described ; or, perhaps, it may be considered as bearing a nearer re- 

 semblance to a fig. Its spongy alcyonic texture is observable, not only 

 on its polished internal, but on its rough external surface; and like 

 the preceding fossils, it appears to have terminated at its lower end in 

 a gradually diminishing pedicle. At the centre of the superior part, 



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