228 Mr. Williamson on the Distribution of 



c. Hard ironshot sandstone 1 ^ feet. 



d. Irregular beds of yellow sandstone, in some parts ironshot 30 



e. Hard ironstone 4 



f. Hard ironstone 8 



(a.) At the bottom of this bed, we find a number of arg'illo-calcareous nodules, 

 resembling- those in the upper alum shale, and containing- Ammonites striatulus. 

 Ammonites, (a new species), Orbicula refiexa, Lingvla Beanii, TerebratuLa 

 bidens, and Avicula echinata? These fossils are chiefly obtained at Blue Wick. 

 No other organic remains occur until within ten feet from the top of this divi- 

 sion of the formation, where a layer of small nodules is met with, enclosing 

 Astacus rostratus, and a new and larger species which has also been found 

 in the clay of the cornbrash. A beautiful specimen of an antenna is in the 

 Scarborough Museum. A little higher in the series is a thin but extremely 

 characteristic seam of Vermetus compressus, also obtained in the coralline or 

 Oxford oolite. 



(6.) Proceeding upwards, we arrive at the series of irregular layers of 

 soft yellow sandstone, throughout the whole of which small fragments of 

 dicotyledonous ? wood, and a species of Belemnites are rather numerous. 

 Towards the top I have found, though rarely, Mija literata, and still higher, 

 two species of Ammonites, one of which resembles A. concavus, which also 

 exists in the upper lias. The other is a new species, which I have named 

 A. inornatus. 



(c.) The next bed, a hard ironstone, contains numerous, small, grey peb- 

 bles, also the same Belemnites as in the seam below, and is characterized by 

 a great abundance of Terebratula trilineata. 



(d.) The beds of yellow sandstone, occasionally charged with oxide of iron, 

 enclose, within a few feet from the bottom, two seams about four inches each, 

 of small pebbles, and at the top is found the same Belemnites as in the beds b 

 and c though sparingly scattered ; the shell resembling Avicula echinata is 

 mingled irregularly with the pebbles. 



(e.) From the hard ironstone bed, though only four feet thick, are ob- 

 tained the greater portion of the fossils characteristic of the inferior oolite on 

 the Yorkshire coast. The following is a list of the principal species, which 

 chiefly occupy the middle and lower parts : 



Trochus granulatus. 



bisertus. 



pyramidalis. 



Solarium calix. 

 Actseon humeraljs. 



Auricula Sedgvici. 

 Nerita costata. 

 Turbo laevigatas. 



funiculatus. 



Rostellaria composita. 



