Dr. FiTTON on the Strata below the Chalk. 1 1 1 



(13.) Other nodules and irregular masses are also found throughout this 

 stratum, which resemble coprolite in their chemical composition, though no 

 traces of animal structure are apparent in them. These are often associated 

 with pyrites, and traversed by veins of that substance, as in septaria. Inter- 

 nally they are in general of a dark brownish hue, and the fracture is even or 

 splintery, like that of some varieties of chert. The form of these nodules 

 is sometimes very like that of coprolites ; but though portions of shells are 

 sometimes found within them, I have not detected any fragments of bone or 

 scales of fishes. The surface of some of the detached masses is eroded, as if 

 by worms ; to the action of which, therefore, they were probably exposed be- 

 fore they were enveloped in the clay. In other cases they are of a very irre- 

 gular figure, surrounding or incorporated with fossil remains, especially of 

 Ammonites, the interior of which is filled with matter of the same kind. 



Concretions of this description occur not only in the gault of different 

 places, but are also numerous in the bottom of the lower green-sand at Ather- 

 field in the Isle of Wight ; and a mass found by Mr. Lyell in the crag at 

 Southwold in Suffolk, which is mentioned by Dr. Buckland*, appears to have 

 been of similar character. The concretions of the gault in Kent evidently 

 agree with those of Havre and Wissant, analysed by M. Berthier, and found 

 to contain about 57 per cent, of phosphate of lime, with a considerable portion 

 also of carbonate of limef . It can hardly be doubted that they are derived 

 from the remains of animals, though no traces of bony texture are now per- 

 ceptible; and it is not improbable that they may have been the contents of 

 the intestines of marine animals, which fed upon each other, though not in 

 all cases moulded into the form of coprolite. 



The abundance of phosphate of lime, especially in submarine strata, will not 

 appear surprising, when it is recollected that not only the bones, spicute and 

 scales of fishes afford that substance in large quantities, but also the covering 

 of the Echinodermata, and of crustaceous animals, in a smaller proportion ;|;. 



* Geological Transactions, Second Series, vol. iii. p. 234, note. 



t Dr. Prout, soon after his examination of the Coprolites, of which Dr. Buckland has given an 

 account in the Geological Transactions (Second Series, vol. iii. p. 237 &c.), was good enough to 

 examine some of the concretions from the gault of Kent and the Vale of Wardour, and from Ather- 

 field, and found them all to contain phosphate of lime, united with carbonate of lime and oxide of 

 iron, in different proportions, the dark-coloured varieties containing the largest proportions of the 

 phosphate. They all, likewise, yielded, more or less, the peculiar smell given out by coprolites 

 when dissolved in muriatic acid. Dr. Turner has since examined other specimens, from the gault 

 beneath Blanc-nez, and at Lottinghen on the east of the Lower Boulonnois, and finds them to indi- 

 cate a similar chemical composition. 



X Hatchett "On Shell and Bone,&c."; Philosophical Transactions 1799, p. 323, and 1800, p. 373. 



