of the Red Limestone of Hunstanton, 241 



position of the Red Limestone would then be evident from the 

 stratigraphical succession alone. 



Thus I have endeavoured to indicate some of the circumstances 

 by which we shall be influenced in forming an opinion on the 

 age of the stratum in question ; and if it has not been absolutely- 

 proved that we must henceforth adopt the absurd name of Red 

 Greensand, some evidence has been produced tending to show 

 that it is not altogether indefensible. It would appear to be 

 newer than any English representative of that rock, and perhaps 

 a little newer than the Tourtia — a name by which it might not 

 inappropriately be known; but as the fossils differ so widely 

 from those of that bed, it may be better, and avoid confusion, if 

 it were named, from its typical exhibition, the Hunstanton 

 Limestone. 



The whole problem is scarcely yet solved, since in Yorkshire 

 there appear to be two red beds, the upper one fairly enclosed 

 in the Lower Chalky rock. What the relations of these beds 

 may be, has yet to be determined ; but, be they whatever they 

 may, the result cannot greatly influence the conclusions here 

 arrived at respecting the age of the bed, since the stratum has 

 been traced almost continuously from Speeton to Hunstanton. 



Some stress has been laid on the difference of mineral cha- 

 racter in the bed at different places ; but that becomes unimport- 

 ant, since Dr. Cookson has lately obtained, from near Hunst^on, 

 fossils in the same mineral matrix as those from Speeton, and 

 Mr. R. Mortimer has noticed that pebbles are found in the 

 limestone near that locality. 



PS. Perhaps nothing has contributed so much to mislead, in 

 the opinions formed on the age of the Red Limestone, as its 

 colour, which appears to separate it clearly from the Chalk 

 above. Its colouring matter is the peroxide of iron. Professor 

 Sedgwick and Sir R. I. Murchison have suggested that this was 

 obtained from the rubbing-up of the Shanklin sands below ; but 

 as, in part of its length, it overlies a clay far distant from any 

 ferruginous deposit, this is very improbable. Moreover, that the 

 bed was not deposited thus coloured is absolutely certain from 

 the abundance and preservation of the fossils ; and hence it is 

 evident that it could only have been coloured by the decomposi- 

 tion of some other colouring matter deposited with it. That 

 this was not a layer of iron-pyrites on the top, is certain from 

 the fact that where the colour is banded it is banded laterally, 

 and not longitudinally as it would have been had the colour been 



Parkinsoni, Inoceramus concentricus, Nucula ovata, Terebratula subundata, 

 Pholadomya decussata, &c. (Leckenby). 



