132 



being filled with the grey flint, a longitudinal section, which would 

 pass through that part, would give a cordiform or cyathiform figure, 

 from this dipping of the matter of grey flint, into the middle of the 

 substance of the alcyonium : and if the alcyonium was formed with a 

 broad base, similar to that which is observable in the specimen, Plate 

 IX. Fig. 4, the appearance yielded by its longitudinal section would 

 perfectly accord with the figure of the inclosed fossil, Plate XI. Fig. 4. 

 The colour of this fossil next excited my consideration, doubting how 

 far this instance would authorize the attributing of this colour, even to 

 other alcyonia of the same species ; but on looking over my collection 

 of these fossils, I found the detached ficoid fossil, purposely introduced, 

 Plate IX. Fig. 8, which exactly agreed in its form with that which in 

 this specimen is involved in the flint. Not only is the red colour very 

 evident in the body of this detached fossil, but it still retains, over 

 great part of its surface, a thin white covering, apparently the re- 

 mains of a similar coat, with that which is seen to surround the alcyo- 

 nium contained in the flint. It is hardly necessary to remark, that 

 the red colour of the animal, blended with the dark semidiaphanous 

 flint, will perfectly account for the purple hue so frequently observa- 

 ble in these specimens. 



The flint stone, Plate XII. Fig. 5, found on the sea-shore, at South- 

 end, in Essex, had often engaged my attention. The curious contex- 

 ture of the plexus of tubuli, of which it is chiefly composed, kd me, at 

 first, to suppose it to be a mass of minute serpulse : this opinion was, 

 however, soon corrected, on discovering, by means of a lens, the fre- 

 quent inosculations of these tubuli. I became then suspicious of its 

 alcyonic nature; and after having attended to the alcyonic flints just 

 examined, was convinced that it owed its form to a substance of this 

 kind: the circular mark of its original cortical investing matter, yield- 

 ing the most corroborating proof that this opinion was correct. 



Just before the plate which this chapter refers to was engraved, 

 the son of that ingenious artist, Mr. Springsguth, to whose labours this 



