482 



THE GEOLOGIST. 



with layers of rag, and are called by the quarrymen, the Cock-beds." 

 The organic remains consist of sponges, zoophytes, Pecten quinque- 

 costatusy and^'a large Terebratula, but these are sparingly found. The 

 beds are twenty-four in number. 



5th. We now come to a succession of beds of chert and sandstone. 

 One bed, about nine inches or a foot thick, is called by the masons the 

 Firestone, and is most probably the equivalent of the rock so-called in 

 Sussex, and described by Dr. Mantell, who denominated the whole of 

 the series as Firestone," but which appears from his description to have 

 thinned out considerably in that locality, and to have become amalga- 

 mated with the chalk-marl. Still, the fossils he describes as belonging 

 to the Firestone at Southbourne are never met with in the Isle of Wight 

 below the Phosphatic Greensand, nor does the chalk-marl ever appear 

 in the whole section of the Undercliff, a distance of nine miles from 

 Shanklin to Blackgary, below the Firestone, or Upper Greensand, as 

 exhibited in his section of the beds near Southbourne.* 



Again, at page 164, he says the ''Firestone contains the same fossils 

 as the Grey marl; " but one, at least, which he enumerates, the Ostrcea 

 carinata, is a characteristic fossil of the two beds, the phosphatic and 

 chloritic greensands, capping the firestone in this locality, and is very 

 rarely found below them. Ammonites planulatus also occurs higher up in 

 the same bed, but I have never met with it in those below. I have 

 merely mentioned these discrepancies with the view of calling attention 

 to the fact, namely, that all the fossils which Dr. Mantell has described 

 and figured in his work on the Geology of the South-east of 

 England," as belonging to the "Upper Greensand," or ''Firestone," 

 belong to the two upper beds of the "Phosphatic Greensand," and to 

 the " Chalk Marl " in this district; whilst neither in the list there 

 appended, nor elsewhere, has he described or enumerated any of the 

 characteristic fossils of these deposits which occur in the Undercliff- 

 series of the Upper Greensand, namely, the Pecten qmnque-costatus, the 

 large Ammonites, Ancyloceras (or Samites), he 



" The Fire-stone group " of Dr. Mantell includes those twenty-four 

 beds above described, but the term is restricted in this locality to an 

 upper bed, about eight inches thick, superimposed on a stratum of rag 

 of a pale blue colour, tinted with red, very hard, about nine inches in 

 thickness, and succeeded by another bed of fire-stone of the same thick- 



* Vide, Maatell's " Geology of the South-east of England," pp. 161—164. . 



