FOSSILS OF THE FIRESTONE. 243 



&c, and of a few genera of simple univalves, as 

 Cirrus, Trochus, Awllana, &c. The bare enumer- 

 ation of the species would occupy a considerable 

 space, and be unintelligible, except to the scientific 

 reader, without the aid of figures. 



There is, however, one fossil which it is neces- 

 sary to describe, from the abundance of its remains 

 which meet the eye in almost every block of fire- 

 stone. It is a species of Siphonia (S.'Websteri), a 

 zoophyte resembling the sponge in its porous 

 structure, but possessing numerous tubular channels 

 that permeate the general mass, and communicate 

 by openings into a central cavity.* This species 

 is in the form of an oblong bulb with a shallow 

 opening, supported upon a long slender stem, 



* Mr.Webster on some new varieties of fossil Alcyonia, Geol. Trans, vol. ii. 

 First series, p. 37C. Mr. Webster mentions that the first specimens showing 

 the connexion of the stems and bulbous part, were observed on some 

 " stupendous and difficultly-accessible masses of rock lying under the ro- 

 mantic cliffs of Western-lines." The branches vary in size from half an inch 

 to three inches in diameter, and from six to eighteen inches in length ; they 

 terminate above in a bulb or head, somewhat resembling in form a closed 

 tulip, and from one to six inches long; the other extremity branches into 

 root-like fibres, by which these bodies, when living, were attached to rocks 

 or stones. If the stems and bulbs are broken transversely, they are found to 

 consist of bundles of longitudinal tubes ; and this internal structure is 

 generally silicified, so that polished sections are very interesting. I need 

 scarcely remind the reader that these bodies have no relation to the Alcyonia, 

 which are polypiferous zoophytes; whereas these fossils are simply a con- 

 geries of tubes and pores, like certain sponges. The fossil that is figured in 

 my "Medals of Creation" (vol. i. p. 259), as Siphonia Websteri, is not that 

 species, but S. piriformis of Goldfuss, which generally occurs in the green 

 sand, but is occasionally met with in the firestone, and in the grey chalk, 

 associated with another common fossil sponge, the Scyphia meandrina. 



