1S6G. ] GODWIN-AUSTEN BELGIAN TERTIARIES. 237 



neous — Corhula pisum, Cancellaria evulsa, &c., have been recognized 

 as such — some, it will be seen, are as yet peculiar, others have been 

 described from imperfect or single specimens ; eliminating these, the 

 remainder are true Crag-shells and also recent species, so that the 

 list no longer presents the admixture of Nummulitic and recent 

 species as was once supposed. 



The Bolderien fauna was considered to indicate a warmer climate 

 than that of the Antwerp Crag {u, s. p. 297) ; but since the pub- 

 lication of Sir Charles Lyell's Memoir, the " Crag Noir," or " Systeme 

 Diestien " has afforded all the forms of Oliva, Conus, Ancillaria, 

 and Cancellaria, from which such conditions were inferred. 



The Bolderberg is the only locality where the evidence of a Bol- 

 derien system, stage, or subdivision has been met with in Belgium. 

 Of the newer formations of the Rhine valley, those of Grafenberg 

 near Dusseldorf can alone, says Beyrich, be placed on the level of 

 those of the Bolderberg ; but he adds that it is very doubtful whether 

 these do not rather belong to the older Sternberg beds or Tongrien ; 

 so that, both on purely geological as on zoological considerations, the 

 Bolderien system may be removed from the general series of distinc- 

 tive geological groups. 



Since the above was written, I have met with the following pas- 

 sage by M. lijst — the result of a comparison of the Edeghem shells 

 with those of the Bolderberg : — " Ce qui nous fait penser que le 

 systeme Bolderien n'est que la base du systeme Diestien de Dumont." 

 It is true that the Bolderberg shells agree with those of Edeghem 

 and Eort Herenthals ; but inasmuch as the Bolderberg shells have 

 been washed out of older beds, the Systeme Bolderien, as an accumu- 

 lation, must necessarily be of later date in the Crag series, and not 

 its base or oldest portion. 



8. General Results. — The study of the Antwerp sections leads to 

 the impression that the vertical dimensions of the whole of the Crag 

 formation there are exceedingly small. Erom the highest ground 

 (ligne culminante) down to the sea-level, the depth is only 9 metres, 

 and within this is comprised the whole formation, including the 

 Campine sands. As it happens in Suffolk*, so here, where the 

 upper or Scaldesien Crag is thickest, the lower is thinnest ; and 

 where the Diestien is thickest, the upper is thinnest, or at times 

 wholly wanting. If the Diestien beds be divided into upper sandy 

 ooze and lower muddy ooze, the sections show that where the first 

 has been removed and " remanie," the resulting Scaldesien beds take 

 the form of " Crag gris ; " and that where it has not, there are then 

 yellowish, argillaceous, and gravelly sands. The real difference be- 

 tween the " Crag gris " and the " Crag jaune " of the Belgian geo- 

 logists is, that the first contains a larger proportion of the "re- 

 manie fauna " of the Diestien beds ; and although they may, as 

 already stated, have been produced under slightly differing condi- 

 tions, and in sequence, yet in the horizontal sections they replace one 

 another, and have not an aggregate thickness of 4 metres. If, as 



* In the Deben valley the Crag does not exceed 25 feet, and even in the Ips- 

 wich district it is of small amount. 



