PRESTWICH BRITISH AND FOREIGN TERTIARIES. 215 



It is more particularly in the lower part of this division, or that 

 portion of it characterized by the Ostrea Bellovacina (Reading and 

 London), that this development of marine forms occurs. Fortu- 

 nately the fossils, though few, are characteristic, and sufficient to 

 establish a very marked analogy with the fauna of the sands of Bra- 

 cheux. It is to this part of the Lower London Tertiaries that I would 

 also refer the lower marine sands of Laon, Rheims, and the sands 

 underlying the travertin of Rilly. In the first place the general 

 relation of these beds of sand to the lignites and fluviatile beds is 

 everywhere the same both in England and France. In East Kent 

 they form, as before said, the lower part of the group which passes 

 at Woolwich under the clays with Cyrena, Melanopsis, Paludina, &c. ; 

 and it is precisely in the same position that they occur in the Beauvais 

 and Champagne districts, for there also they clearly underlie beds of 

 fluviatile clays and lignites. Neither is there any discordance in the 

 mineral characters. In East Kent the sands are quartzose, sometimes 

 nearly white, and at others much mixed with green sand with a few 

 flint pebbles. In the Beauvais district they also consist of a base of 

 whitish quartzose sand, more or less mixed with grains of green sand, 

 occasionally coloured in parts by the oxide of iron, and likewise 

 containing some flint pebbles ; they there merely exhibit in addition 

 slight traces of carbonate of lime. As the sands range into Cham- 

 pagne, they become rather finer, the green particles fewer, and therefore 

 the mass is often formed of a nearly pure white quartzose sand, 

 especially where it has been subjected to the washing process which 

 accompanied the deposition of the Rilly travertin, wherever that bed 

 overlies the sands. In addition to these common mineral and palseon- 

 tological features, there is a common physical feature maintained 

 throughout their range, one of no importance separately, but of some 

 value conjointly, viz. the presence of rounded and much- worn flint 

 pebbles sometimes scantily scattered through these sands, at other 

 times arranged in bands, chiefly at their base. (Diagram, str. e,f, n.) 



The fossils are dispersed, as in the English series, in patches, and 

 rarely form continuous or widely-extended bands. The lists of or- 

 ganic remains given by M. Graves* and M. Mellevillef enable 

 us now to compare the fauna of the Beauvais and Champagne sands;};; 

 with that of the Woolwich Sands of East Kent. I should observe, 

 however, that in this country these organic remains are far from being 

 worked out so fully as in France, for, with the exception of the col- 

 lection made by Mr. Lay ton and myself at Richborough, and by my- 

 self at Heme Bay and Oakwell, no fossil-examination of these beds 

 has taken place ; at the same time their limited development under 

 marine conditions in England, and their peculiar mineral characters, 



* Op, cit. p. 196. 



t " Memoire sur les Sables Tertiaires inferieurs du Bassin de Paris." (Annales 

 des Sciences geologiques, vol. xi. 1845, p. 9-13.) 



% M. Rondot also gives a list of some of the characteristic species (" Etude 

 Geologique du Pays de Rheims," Ann. de I'Acad. de Reims, annee 1842-43). 

 M. Hebert makes a further addition to the Rheims fauna, and states that the 

 number given in M. Melleville's list is far from being complete (Bull. Soc. Geol. 

 2nd Ser. vol. vi. p. 729-730). 



