Mr. Rose's Sketch of the Geology of West Norfolk. 181 



The well at the school-house at Bilney passed through the 

 same series of strata, but at this locality the gray limestone 

 inclosed Inoceramus g?ypha?oides and Belerrmites minimus; the 

 clay contained the same Belemnite,and &\so Belemn. attenuates. 

 From an old clay pit near Pentney church, I took the above 

 two species of Belemnites : this is, I believe, the spot referred 

 to by Smith on his map; the gray limestone has not been 

 exposed at this place. 



I shall here describe the red chalk of Hunstanton as the 

 equivalent of the gault. It is a compact limestone coloured 

 by oxide of iron, containing many small dark-green siliceous 

 pebbles, and is divided into two beds : the uppermost, about 

 seven inches in thickness, abounds in organic remains ; this 

 bed is intersected throughout by a ramose Zoophite, the na- 

 ture of which is not satisfactorily determined ; and the two 

 characteristic species of Belemnites are in great abundance ; 

 Terebratula biplicata and Inocerami are numerous, and one 

 species of Nautilus occurs. The lower bed is three feet five 

 inches in thickness, contains less of the Zoophite, and fewer 

 fossils than the upper, but the siliceous pebbles are more nu- 

 merous. I have not been able to trace these beds inland be- 

 yond Heacham. 



A seam of dark red argillaceous matter, two to three inches 

 in thickness, separates these beds from the incumbent white 

 beds. Upon analysis it proves of the nature of fullers' earth, 

 so highly coloured with oxide of iron that it has been used as 

 a pigment. 



The paucity of genera among the organic remains at pre- 

 sent discovered in this stratum is not to be wondered at when 

 we compare its thickness with that of the Cambridge gault. 

 With us little more than fifteen feet* is probably its utmost 

 depth : at Cambridge it is said to be 150 feet : but it must not 

 be supposed that all its contents have been seen, for but few 

 perforations have been made where any attention has been 

 paid to its contents. 



The gault of Norfolk affords a remarkable example of dis- 

 similarity in the mineralogical character of adjoining portions 

 of a contemporaneous deposit, and is an additional illustration 

 of the necessity for employing the zoological character to 

 determine their identity. Without consulting these " medals 

 of Nature," who could imagine that the red limestone of Hun- 

 stanton Cliff, and the blue gault containing gray limestone at 

 Pentney and Bilney, were deposits of the same epoch ? 



* The boring of a well at Diss extends it to twenty feet. [See a notice 

 of Mr. John Taylor's paper on the strata penetrated in sinking a well at 

 Diss, in Lond. and Edinb. Phil. Mag., vol. v. p. 295. — Edit.] 



