90 peop. j. peestwich on" the coeeelatioit oe the 



Calcaiee de Mons* 



"With this formation there is no difficulty. It is not represented 

 either in England or in France, unless, as suggested by some of the 

 French geologists, the Strontianiferous Marls of Meudon, with which 

 it has two species in common, or the Calcaire Pisolitique of Mont 

 Aime, be related to it (see list). It is almost equally distinct from 

 the overlying Tertiary strata as it is from the Maestricht Chalk. 

 It seems to be a passage-series, though connected with the Tertiary 

 by ail the genera, and a few species, of its MoUusca. 



Notwithstanding its local importance, it has a very limited range, 

 being confined to a small district near Mons, where it underlies the 

 Lower Landenian, and attains in one place a thickness of above 300 

 feet. It contains a rich Molluscan fauna of above 100 species of 

 Lamellibranchs *, and nearly 300 species of Gasteropods, which 

 latter have been described by MM. Briart and Cornet f. The 

 general facies of the fauna resembles that of both the Lower and 

 Upper Eocene, though only 22 species of the Gasteropods are com- 

 mon to the two series. The others are new species peculiar to this 

 deposit, but all the genera are Tertiary forms. 



The species described by MM. Briart and Cornet as being common 

 to the Calcaire de Mons and to strata of Eocene age elsewhere are 

 given with their range, according to Deshayes and the above authors, 

 in the following list : — 



Actaeon (Tornatella) parisiensis, Desk., 



c. c Lower Landenian; Sables Inferi- 



eurs, Sands of Chalons-sur-Vesles. 



Adeorbis similis, Desk., r Sables Inferieurs, HerouvaL 



•Tj • , 1 .-, T7- f Lower and Upper Eocene of the Paris 



Buccmum stromboides, ^™ ^^^.^ Bri^eUian and Brackle- 



(Jaiyptraia trocmtormis, iya^^iA'., r , ' 



suessomensis, D' Orb Lower Landenian; Sables Infe- 

 rieurs |. 



•Ceritbium inopinatum, Desk. Conglomerate (Lignites) of Meudon. 



striatum, Srug Upper Eocene of the Paris Basin. 



unisulcatum, Lamk., var. A All the Eocene strata of the Paris 



Basin. 



Cometia modunensis, Mun.-Chal., c. ... Strontianiferous Marls of Meudon §. 



Cylindrellina Briarti, ilfMw.-CAa^., r. ... Sands of Jonchery? (Sables Infe- 

 rieurs). 



Melanopsis buccinoidea, Ferussac Lignites ; Sables Inferieurs. 



Natica infundibulum, Watelet Sables Inferieurs. 



parisiensis, Desk Upper Eocene of the Paris Basin. 



Wateleti, Desk Sables Inferieurs. 



Oliva mitreola , Lamk., r Sables Inferieiirs ; Calcaire Grossier. 



Pyramidella eburnea, Desk Calcaire Grrossier. 



Turbonilla acicula, Xam,^ All the Eocene Strata of the Paris 



Basin. 



* These have not yet been described. 



t Mem. de lAcad. Eoy. de Belgique, 1871-1877. 



\ The term " Sables Inferieurs " embraces all the strata in the Soissonnais and 

 Laonnais between the Chalk and the Calcaire Grossier, including the sands of 

 Chalons-sur-Vesles, Brimont, Laon, Herouval, Aizy, Jonchery, Sainceny, Cuise- 

 la-Motte, &c. 



§ I should be disposed to refer all the Lower Tertiaries at Meudon to the 

 eame zone as the Woolwich and Beading series, but on this point I speak with 

 hesitation. 



