M M. D'Omalius D'Halloy on 



tant countries, as le Berry, Lorraine, the Boulonais,* the 

 coast of Calvados, &c. This limestone is every where dis- 

 tinguished by its tenacity, by its spathose parts, or by a tex- 

 ture which, without being spathose, nearly approaches the 

 crystalline state, by the abundance of its fossils, which afford 

 besides the oysters of the Pays de Bray, other species of a 

 considerable size of the family of the ostracae and of that of 

 byssiferi, trigoniae, a great quantity of zoophytes, particu- 

 larly madrepores, &c. This limestone is always in the neigh- 

 bourhood or accompanied by the clay below the chalk ; its 

 geological position is no where better seen than at the cliff 

 named Vaches Noires, on the coast between Honfleur and 

 Dives (Calvados). It there forms some beds more or less 

 thick, situated between two systems of grey marly clays. 

 The superior system often contains blackish green grains of 

 chlorite, and passes into the chalk with chlorite, which is 

 immediately above it. The inferior clay is characterized by 

 great and wide gryphites (gryphaea latissima),+ and rests 



* The major part of the Boulonais consists of the same formations as 

 the Pays de Bray; it is only in the northern portion that from beneath 

 these rocks rise successively, the coarse horizontal limestone, then the 

 marquise marbles, which I consider as belonging _to the older alpine 

 limestone, or zechstein of the Germans, and lastly the coal measures. 

 The latter dips again under the chalk, which borders this little region 

 by a chain of hills in the form of a semi-circle. It is right to remark here 

 in consequence, that I committed a mistake, in 1808, (Journal des Mines, 

 tome 24, p. 348) by referring the Boulonais limestone, which I had not 

 myself seen, to the transition formations, abundant in the north-west 

 of France. 



f Coral rag, which rises from under the superior rocks, at Henque- 

 ville cliff (between the Vaches Noires and Honfleur), and forms the top 

 of the hill on the east of Benerville, fines off on the eastern part of th,e 

 Vaches Noires; the following is a section of this cliff a little to the west 

 of Oberville, beginning with the surface. 



Green sand formation 



Limestone (inferior to coral rag) 



Whitish marl 



Thick ooUte bed 



Oxford clay. 

 Tlie gryphosa latissima is, I suppose, the gryphsea dilatata of Sowerby, 

 which I observed to be most abundant there ; for further particulars and 



