166 UPPER, OR FLINTY CHALK. 



tomosing depressions, surrounded by a circular or elliptical indentation, 

 that forms the outer margin. These markings are produced by the edge 

 of the porous substance enveloped in the flint, which is evidently the re- 

 mains of a zoophyte of the genus Spongus. 



The body is from one to three inches in length, apparently smooth, 

 but giving that peculiar sensation of roughness to the touch, which is con- 

 sidered by Mr. Parkinson, as characteristic of the fossil remains of the 

 spongige and alcyonia. 



Some specimens are sohd, others hollow, or partially filled with a hght 

 porous mass ; and in numerous instances the interior is lined with mamil- 

 lated chalcedony of an azure colour. 



Localities. Upper chalk, near Lewes. 



16. Cylindrical bodies enclosed in flints. 



These are the remains of unknown zoophytes, in which but few traces 

 of organization are preserved. They are of a cylindrical form, from one to 

 six or eight inches in length, and about half an inch in diameter. They 

 consist of flint, and are invested with a thick covering of the same : the 

 interval between the surrounding flint, and the enclosed fossil, being either 

 hollow, or filled with a chalky porous substance, in all probability the de- 

 composed remains of the epidermis of the original. In one specimen the 

 cylinder is traversed by longitudinal tubes. 



Localities. Very abundant in the chalk, and on the ploughed lands 

 near Lewes. 



17. A compressed zoophyte, having a finely reticulated surface. 



The remains and impressions of this fossil are invariably of a ferrugi- 

 nous colour, and are of frequent occurrence in the chalk. The specimens 

 are from 0-1 to 0-2 inch in thickness, and extend in the manner of the 

 goj'gonia, oftentimes covering a space of six or eight inches square ; but 

 no perfect example has hitherto been discovered. Both the external and 

 internal surface is covered with minute pores, regularly disposed, which 

 when viewed through a lens, prove to be the meshes or openings of a 

 reticulated plexus of fibres ; the intermediate substance is composed of 



