12 GEOLOGICAL MEMOLRS. 



rock of the texture of sandstone, very slightly calcareous, of a red colour on the 

 outside, but a whitish grey in the fresh fractures : this rock contains numerous 

 fragments of indeterminable fossils ; its present position seems to be the result 

 of a reconstruction. 8 inches to 12 inches. 



7. Yello^^isll or white limestone of a coarse texture ; some of its bands are 

 compact, others very friable ; in it occur certain beds, and detached fragments, 

 of a very hard white rock, f inch to 5 inches thick, entirely soluble in acids, and 

 some of them containing numerous cavities full of a pulverulent lignitic matter. 



The appearance of some of the hands of the limestone reminds 

 one of the '' tufFeau" of Ciply and Maestricht ; but the difference in 

 their mineralogical texture is easily detected. The palaeontological 

 evidence, however, leaves no doubt in this respect. An enormous 

 quantity of fossils, in a perfect state of preservation, has been pro- 

 duced from all the beds of the limestone, and even from the beds and 

 detached fragments of the harder included limestone. From 140 to 

 150 species have been collected, of which a great number appear to 

 be new. Of the known species, not one is Cretaceous ; ^' all belong 

 to the Tertiary beds above the Glaueonie inferieure of M. d'Archiac 

 and the Sables de Bracheux of the Prench geologists." 



The following is the list of the fossils which the authors have 

 determined : — 



LAMELLIBRAJfCHS. 



Cytherea multisulcata, Desh. 

 Cardita planicosta, Lam. 

 Crassatella compressa. Lam. 

 Corbula striata. Lam. 

 Corbis lamellosa, Lam. 

 Area biangula, Lam. 



modioliformis, Desk. 



Tellina rostrahs, Lam. 



donacialis, Lam. 



Lucina mitis. Sow. 



Gasteropods. 

 Turritella intermedia, Desh. 



imbricataria, Lam. 



Voluta spinosa, Lam. 

 Ancillaria buccinoides, Lam. 

 Mitra terebellum, Lam. 

 Cerithium uni sulcatum, Lam. 

 Melanopsis buccinoides, Fer. 

 Buccinum sti'omboides. Lain. 

 Nerita Caronis, Brong. 

 Natica perforata, Lam. 



epiglottina, Laoii. 



Monodonta Cerberi, Brong. 



The greater number of the species which appear to be new be- 

 long to the genus Nematura, and some others to the genera Ancil- 

 laria and Auricula. 



The authors then describe and compare several sections in the 

 neighbourhood of Mons, by which they endeavour to prove that the 

 glauconitic sand (no. 5) met with above the fossiliferous limestone 

 of the well of M. Goffint represents the base of the Landenien infe- 

 rieur, and corresponds to the beds of Angres and Tournay with 

 Plioladomya Koninckii. 



Detailed sections at Ciply, Nimy, and other localities are given, 

 a complete section of which would represent the beds in the following 

 ascending order, resting upon an eroded surface of the chalk: — 



1st. A very glauconitic sand, shghtly argillaceous. In its lower 

 part the grains of glauconite are comparatively small and numerous, 

 and are imbedded in a matrix of a whitish-blue substance, which 

 gradually becomes softer towards the upper part, while the grains of 

 glauconite become larger and less numerous. To the south-west of 

 Mons it contains Plioladomya Koninchii, more or less abundantly, 

 and at Ciply a fossil of the genus Area has been discovered. 



