COOKE : LOWER OOLITES OF SCARBOROUGH. 291 



henleyi, Lima peciiniformis, Pecten demissus, Goniomya v. scripta, 

 Trigonia scarb urge ns is , Terebratula lagenaiis, Exogyra nana, Gryphea 

 mima> Homomya crassiuscula, several species of Pholodomya and 

 Myacites, Serpula intestinalis, Vermicularia nodus, and many others 

 which, though plentiful, are not quite so common as the foregoing 

 A complete list of the fossils collected and observed in this section 

 is appended. 



In many of these fossils the carbonate of lime of which the 

 shells were originally composed has been wholly or partially replaced 

 by carbonate of iron, and this latter by subsequent oxidation has 

 been converted into a hydrous peroxide. 



Sub-division r, which is the predominant feature of the Scar- 

 borough Cornbrash, consists of an exceedingly compact, semi- 

 crystalline limestone, having a fairly uniform thickness of about 

 four feet. It crops out along the quarry face, and stands out in 

 bold lines from among the shales with which it is intercalated. 

 Owing to its great compactness the pitmen have to use dynamite 

 when quarrying it, and it is from the masses and fragments that 

 have been thus detached that the Iithology and fossil contents may 

 best be studied. The rock is crowded with fossil remains, but the 

 task of removing them is a difficult and often an unsatisfactory one. 

 Many of the fossils are of a black or of a blue-black colour, which 

 is probably due to the presence of phosphate of iron that has been 

 formed by the decay, by bi-carbonate of iron, of the pre-existing 

 phosphate of lime. This bi-carbonate would be formed by the 

 reaction of iron-oxide and the carbonic-oxide derived from the 

 decay of the organic matter of the fossil. 



The rock is variously coloured on the weathered faces, but the 

 interior is always light blue or ashen-grey. These tinctorial varia- 

 tions are due to the different decrees of oxidation which the iron 

 contained in the beds has undergone, the yellow being often due to 

 the formation of a sesqui-oxide and the red or fawn to a per-oxide. 

 When freshly broken the surfaces of the fractures are clean and of 

 a blue colour ; but on exposure the surface weathers rough and the 

 colour changes to an ochreous red or an ashen grey. 



The contained fossils are both generically and specifically very 

 numerous, and are identical with those found in the overlying sub- 

 divisions. 



There are, however, one or two points of interest in connection 



The first of these is the noting of the occurrence 



ipecial 



form cephalopod which I obtained from this bed. It has nothing in 

 common v th the Nautilus hexagonus which lies in the Scarborough 



Wl^^ l lW ■— M B ■!* j | I I I— W l I — 



Oct, 1896. 



