106 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



with regard to the relative richness of each fauna ; and also, whilst 

 almost each genus presents some species in common, the other species 

 are constantly representative forms. The principal exceptions are — 

 in the instance of Turbo, Trochus, Pileopsis, and Delphimda, of each 

 of which there are but 3 species in England, whereas in France 

 they are exceedingly numerous ; — the absence here of Venus, Donax, 

 and Corbis ; — and the presence of a larger proportion of reptiles and 

 fishes. 



§ 3. The Belgian equivalent of the Calcaire grossier and Brackle- 

 sham Sands — the Bruxellian System. 



Owing to the want of sections in Belgium it is very difficult to 

 follow the succession of the strata. The zone of the Nummulites 

 planulatus appears to be well marked, and to correspond with the 

 Lits coquilliers and associated sands in France, and with the Lower 

 Bagshot Sands in England. 



Above this there is, near Brussels, a stratum of siliceous sands 

 about 40 feet thick, considered to form the lower part of the Bruxel- 

 lian System. To this succeed, in ascending order, 30 to 40 feet of 

 sands with sandstone-concretions ; then a more calcareous greenish 

 sand, 10 feet thick, containing many fossils, and overlaid by 2 feet of 

 sands with Nummulites Icevigatus, and 20 feet of fossiliferous sands 

 with calcareous concretions, — making a total thickness of about 100 

 feet. The fossils are confined chiefly to the upper portion of this 

 formation ; and the strata decrease in importance as they range 

 northward. 



This series of strata seems to represent exactly the Calcaire grossier 

 of France and the Bracklesham Sands of England. It contains a 

 large proportion of fossils common to both countries, of which the 

 most characteristic species are — 



Acteon sulcatus, Lam. Natica epiglottina, ham. 



Area barbatula. Lam. labellata, Lam. 



Cardita decussata, Lam. patula. Desk. 



Cardium porulosum, Lam. Nummulites laevigatus. Lam. 



Cassidaria carinata. Lam. Ostrea flabellula, Lam. 



Conus deperditus, Brug. Pecten plebeius, Lam. 



Corbula gallica, Lam. Rostellaria ampla, Brand. 



— rugosa, Lam. Solarium patulum. Lam. 



Cyprfiea inflata, Lam. spiratum, Lam. 



Fusus Noa?, Lam. Tellina teniiistriata. Desk. 



Lucina sulcata, Lam. Turritella terebellata, Lam. 



gibbosula, Lam. Venericardia planicosta. Lam. 



Mactra semisulcata. Lam. Voluta cithara. Lam. 

 Melania raarginata. Lam. 



Both Sir C. Lyell and M. Omalius D'Halloy give lists of the fos- 

 sils from these beds. The one enumerates Q7 species, and the other 

 92*. Of these, 82 species are peculiar to the Brussels beds, and 



* As M. 0. D'Halloy gives no sections, I cannot feel sure that his division 

 corresponds exactly with that of Sir Charles Lyell. 



