194 EEV. J. F. BLAKE ON THE 



No. 1 is a creamy limestone, with Trigonia gihhosa and Pecten 

 lamellosus, about 9 feet 6 inches thick. It has yielded a Brachiopod 

 like Waldheimia holoniensis. 



No. 2 is a vacuous bed, like the roach, with casts of the Trigonia 

 and Perna mytiloides, 4 feet 8 inches. 



No. 3 forms parts of No. 2, but is clearly separated below. It is 

 an oolite with a shell-band, with Pernoe towards the top and bottom, 

 5 feet. 



These three are the only possible representatives of the building- 

 stones. In the absence of flints and in the character of the rock 

 there is similarity. In the want of the characteristic shell, Ceri- 

 ihium portlancUcum^ and the abundance of the Pecten and Perna 

 found in Portland on lower horizons, there is so much difference as 

 to lead to the conclusion that these are either continuations of the 

 flinty series or deposits in a separately eroded, area. 



PoUowiug these are : — 



No. 4. A brownish-weathering, suboolitic block, 8 feet in thick- 

 ness, the upper part full of Trigonice, and a few flints near the 



No. 5. A band of flinty rock, varying from 2 feet 6 inches to 

 4 feet, with an irregular base filled with indurated clay. 



No. 6. A solid suboolitic rock, 8 feet 6 inches thick. The grains 

 are very coarse, and broken shells very numerous, with Trigonice. 



These appear to represent the base-bed and J'W^/ojwa-bed of the 

 island under a slightly different form. The latter were deposited on 

 an eroded surface formed at the expense of the succeeding rock. 



This, No. 7, is a valuable building-stone, for which the quarries 

 are worked. It is a fine-grained suboolitic rock, with few fossils, 

 rather flinty towards the base, and about 10 feet thick ; it is fol- 

 lowed by 



No. 8. A brown sandstone, 1 foot 6 inches. Had these occurred 

 in the island, they would doubtless have been worked towards the 

 north-east corner; but they occupy the interval bett^een No. 5, the 

 Trigonia-hed, and No. 7, the Serpulite, of the typical section, 

 though they are scarcely equivalent to No. 6, which represents the 

 result of their contemporaneous erosion. 



No. 9 may be taken as 16 feet, all of which is very flinty ; it is 

 full of fucoids, and has, towards the middle part, as great an abun- 

 dance of Serpula gordialis as at Portland. Ammonites holoniensis 

 is also abundant. 



No. 10 constitutes the main mass of the flinty series, and forms the 

 capping of St. Alban's Head and the cliff facing west. It is not very 

 accessible ; but I have measured 50 feet, which^includes a shell-bed 

 at the base, like that in Portland ; the rest is very unfossiliferous, 

 and, after exposure to the sea, has much the aspect of a calcareous 

 grit, there being much siliceous matter even between the flints. 



A comparison of the total result at this spot with that in Port- 

 land shows that the only possible representative of the building- 

 stone is swollen to 19 feet by the addition of a higher bed (if this 

 be the right interpretation), while the flinty series has expanded to 



