JURASSIC OF THE PARIS BASIN. 



557 



Portland" than it is at Boulogne. The fossils of these cement-stones 

 are abundant; they are Ammonites suprajurensis, Natica athleta?, 

 Pleuromya sinuosa, Thracia incerta, Cyprina elongata, C. implicate: ?, 

 Trigonia (clavellate sp.), Mytilus autissiodorensis, and Anomia laevi- 

 gata. The lithological character of these limestones, and the abun- 

 dance of Mytilus autissiodorensis and of Thracia incerta, lead one in 

 the first instance to recognize in these beds the cement-stones at the 

 base of the Portland sands ; but in face of the abundance of Ex. vir- 

 gula and the presence of Amm. suprajurensis, it is safer to look upon 

 these as the more marly portions of the " Lower Portlandian," such 

 as are associated with the conglomerates at Portel and are abundant 

 with the same fossils in Kimmeridge Bay. These cement-stones 

 are cut off from less fossiliferous marly beds above by an inter- 

 mediate bed of " Calcareous Grits with Anomice." These two, with 

 the k ' Glauconitic Calcareous Grit" and " Upper Conglomerate" form- 

 ing the cap, will then represent the uppermost portion of the Bolonian 

 " Lower Portland " Avith Pteroceras oceani. That fossil is not recorded 

 from the Pays de Bray ; but the occurrence of Trigonia boloniensis, 

 Pecten nudus, and a Hemicidaris called H. Hofmanni, but perhaps 

 really H. purbechensis, is highly characteristic. Of the upper beds 

 little is now visible. The blue marls, described by de Lapparent as 

 dark at the base, with Oardium morinicum and large Ammonites 

 (? biplex), and calcareous towards the top, with Amm. biplex, Pleu- 

 rotomaria JRozeti, Ostrea expansa, Perna Bouchardi, and Cardium 

 Pellati, are obviously representatives of the " Middle Portland" beds 

 of Boulogne, and are more similar to them than to the corresponding 

 English series. Finally the ferruginous sands seen at Gournay are 

 certainly distinct in appearance from any thing seen elsewhere : and 

 they contain few if any fossils. At their base, however, they contain 

 huge calcareous-grit doggers, which resemble very much those of 

 Swindon and Shotover, the corresponding beds at Boulogne being 

 more regular and calcareous. These contain clavellate Trigonice, 

 Astarte, Corbula, and Thracia incerta ? It is above these beds that 

 ferruginous nodules are found, which contain Trigonia gibbosa and 

 other true Portlandian Trigonice, e. g. T. incurva, the specimens of 

 which from the JN T ormanville cutting, near Gaillefontaine, preserved 

 in the Ecole des Mines at Paris, are undoubtedly the true forms, 

 though they can no longer be found in a recognizable state. While, 

 therefore, the lower part of the sands and grits may well be the 

 equivalents of our " Portland Sands," the upper part must at least 

 attain the horizon of the Elinty series of Portland. 



Y. The Bouloknais. 



The coast of this district is almost English ground : so well is it 

 known, and so long has it been studied by many of our native geolo- 

 gists. They have, however, published little upon it ; and we owe the 

 description of the area first to M. Eigaux (33) and Prof. Hebert 

 (37), and later to MM. de Loriol and Pellat (36, 39, 41, 56, 61), 

 the last-named author having given a final resume of his views in 

 1878 (68). M. Pellat's classification is now as follows : — 



