186 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 10, 



Pentacrinus (ossicles), Dixon, Foss. Flabellina. 



Sussex, pi. 20. f. 6a, 7 6. Nodosaria Zippei. 



, ibid. pi. 19. f. 15. Marginulina ensis. 



Agassizii, ibid. pi. 19. f. 3a. Cristellaria rotulata. 



Cidaris sceptrifera aad others. Dentalina. 



Asterias and Ophiura. Spirolina irregularis. 



Pollicipes maximus and others ? lagenalis. 



Bairdia subdeltoidea. Lituola nautiloidea. 



Cytherella ovata. Ventriculites. 



Frondicularia Verneuiliana. Many species of Bryozoa. 



Archiaciana. Fish teeth (Larana, &c.). 



Tertiary. 

 Potamomya. Bryozoa. Fish bones and teeth. 



Land and Freshwater Shells from Bed Ko. 5. 



Zonites rotundatus. Valvata piscinalis. 



crystallinus. Bithinia tentaculata (chiefly oper- 



nitidulus. cula). 



Carychium minimum. Odostomia ? 



The bed No. 4 consists of blue clay, containing a large quantity of 

 calcareous matter. It is about 11 feet in thickness, and its sur- 

 face is undulated throughout. At the southern part of the eastern 

 excavation this bed passes upwards into a yellow clay (4^, in the Sec- 

 tion) 6 feet thick, with numerous small, irregularly rounded concre- 

 tions of carbonate of lime ("race" of the workmen). In a section 

 opened in the southern part of the field in 1836*, and separated 

 from the eastern section by a strip of ground that is not worked, 

 consisting probably of bed No. 5, and forming as it were a ridge 

 trarersing the field from E. to W., appears a yellow, sandy clay (4^, in 

 the Section), laminated, about 10 feet thick, dipping to the south, 

 and there passing into, and alternating with, similar clay of a blue 

 colour. In this laminated yellow clay are found numerous thin 

 calcareous concretions, flat, and irregular in shape f ; as well as a few 

 of the roundish calcareous bodies, above mentioned. The yellow clay 

 rests on a sandy gravel (5^ in the Section) ; towards the surface it 

 sometimes contains much chalk-debris ; and at places it is seen to 

 pass upwards into an obscurely laminated brown loam. In the west- 



* See Loudon's Mag. Nat. Hist. vol. ix. p. 429. 



t See Loudon's Mag. Nat. Hist. 1836, vol. ix. p. 430. The following observa- 

 tions on the " Race," both from the laminated and the non-laminated clays, have 

 been kindly supplied by H. C. Sorby, Esq., F.G.S. When a portion of the soft 

 part of one of the subglobose bodies above referred to is spread in water and exa- 

 mined under a high power with polarized light, it is seen to consist of fine grains 

 of quartz-sand, mica, more or less decomposed felspar, peroxide of iron, and a 

 large proportion of calcareous particles. The greater part, if not the whole, of 

 the calcareous particles appear to have been derived from chalk ; for numerous 

 characteristic fragments of the Foraminifera, of which that deposit is almost 

 entirely composed, are found in it. The harder portions, and a considerable pro- 

 portion of the soft, present such characters as render it almost certain that they 

 had a similar origin, but that they have since undergone a considerable amount 

 of crystalline consoUdation ; and this is especially the case with the hard, flat 

 pieces, which have a waterworn appearance, whose structure is identical with the 

 harder parts of the rounder and softer ones. On the whole, I am of opinion that 

 they were formed from a mixture of chalk and fine clay, and that they have since 

 been consolidated by the action of carbonic water ; and this process, having in 

 some cases proceeded from certain centres, has given rise to the nodular portions. 



