OSBORNE BEDS. 155 



building stone. This change of mineral character apparently 

 escaped the notice of Professor b^orbes, who has described the 

 bed, both under its normal and altered aspect, in his section of the 

 Nettlestone Grit, at pages 74 and 75 of his memoir on the Fluvio- 

 marine formation of the Isle of Wight, as two distinct and separate 

 strata, Nos. 9 and 10. 



The following is Forbes' detailed section of the beds in the 

 centre of this anticline : — 



(1. St. Helen's Sands.) 



1. Immediately under the lowest bed of the Bembridge Lime- 

 stone (here 'livided into three bands) occurs a band of dark 

 greenish carb- naceous clay, breaking with a sub-conchoidal 

 frac^-ure, and forming a truncated stratum in the clifF; 1 ft. 6 in. 



2. Pale greenish white and yellowish marls, with patches of 

 calcareous sand and comminuted shells ; also argillo-calcareous 

 nodules of various sizes. In this bed a characteristic fossil, 

 Melania excavata, occurs in abundance, and has the shell 

 preserved. 8 ft. 



3. Pale green, yellowish, and white sands, hardening into sand- 

 stones, with large lenticular siliceous concretions and spono-oid 

 bodies. Melania excavata is plentiful here and there, and 

 occasionally occurs crowded. A small Hydrohia is also present ; 

 and from a mass of loose sand I extracted a Helix with the shell 

 entire, apparently Helix omphalus, but unfortunately destroyed 

 the specimen. 14 ft. 



4. Greenish-yellow irregular and concretionary sandstone, with 

 siphonoid or fucoidal bodies ; 3 ft. 



5. Yellowish and whitish sands, with a line of purple (mano-a- 

 nese ?) nodules and siliceous concretions below ; 9 ft. 



6. Laminated white sands, indurated into quartzose flao-s above 

 and below ; the upper surface exhibiting strong current marks. 

 This band is remarkable for its contents, including Limncea 

 longiscata, a shorter species of Limncea, resembling X. pereqra 

 Planorbis obtusus, and Melania excavata, all in the condition of 

 casts. The fossiliferous portion is in the lower part. 3 ft. 



7. White sandy clay, with a band of broken Cyreiice ; 2 ft. 



8. Greenish-blue clay, seen on shore at low-water, containing 

 Cypridce and traces of Melania and CyrencB (C. obovataT). The 

 thickness may be estimated at 8 ft. [This apparently contains 

 the fish-bed discovered by Mr. Colenutt.] 



(2. Nettlestone Grits.) 



9. Imperfect softish bright yellow limestone, riddled by minute 

 confervoidal cavities, hardening into a building stone by exposure 



