370 Revieics — E. Rigaux on the Boulonnan. 



11. — Notice Geologique sur le Bas Boulonnais. Pai- E. Ktgaux. 

 Extrait du XIV*^. vol. des Memoires de la Societe Academique 

 de Boulogne. 1892. 



THIS is the second edition of a work published by the Boulogne 

 Society in 1865 ; it is now revised and augmented — many 

 additions being due to the labours of Gosselet, Pellat, Douville, de 

 Loriol, and Cossmann. It is, perhaps, unusual for an Academic 

 Society to issue a i-evised edition of a Memoir, but the proceeding 

 in the case before us is one to be commended, as the information 

 regarding a particular area is summarized and brought up to date. 



The strata exposed in the area include the Devonian, Carboniferous, 

 Jurassic, and Cretaceous ; Silurian rocks have also been proved in 

 several places beneath the Secondary strata. 



The author gives an account of the principal stratigraphical 

 divisions of each formation, notes the fossils found at different 

 horizons, and gives some general lists of species. He has not 

 followed the fashion of subdividing all the strata into zones, and in 

 many respects his plan is more satisfactory, as the facts are thus 

 clearly stated, and general comparisons can be made with the 

 fossiliferous horizons in other places by those desirous of doing so. 



The Devonian rocks commence with the Givetian stage, which 

 includes slates, conglomerates, and grits, overlaid by limestone 

 (Calcaire de Blacourt) with Stringocephalns Burtini, etc. Then 

 comes the Frasnian stage, divided into the (1) Beaulian and (2) 

 Ferquian sub-stages ; they include a series of slates and limestones 

 with Spirifer orbeliaims. Chonetes Douvillei, Pentamerus hrevirostris, 

 StreptorhyucJins Boucliardi, S. elegans, and Bhi/nchonella puyniis, in 

 the lower division ; and Athyris concentrica, Strophomena latissima, 

 and Chonetes armata in the upper division. Common to these two 

 divisions are Spirifer Veriieuili, Atrypa reticulnris, etc. The highest 

 stage, the Famennian, includes grits and slates with Bellerophon 

 hilobatus, CucuUcBa trapezium, etc. 



Carboniferous rocks i-est conformably on the Devonian, and include 

 two divisions, (1) Limestone, and (2) Coal-measures. The Carboni- 

 feroiis Limestone comprises lower beds with Productus Cora, middle 

 beds with Productus unddtiis, Spirifer ghther, Bliynchouella pleurodon, 

 Terebratnla hastata, etc., and upper beds with Productus giganteus, 

 P. semireticulatus, Athyris Boissyi, etc. The Coal-measures are 

 shown at the surface in but few localities ; the beds have been 

 much disturbed, and, as proved by borings, older rocks have in 

 places been thrust over them. 



Resting directly on the Palfeozoic rocks in this area, as under 

 London, there are found strata of Great Oolite age. Beds grouped 

 as Bathonian, and representing the upper part of the Great Oolite 

 (Forest Marble, etc.) and Cornbrash are described, and a long list of 

 fossils is given. 



The Brachiopoda are curiously placed, both in this list and in that 

 of the Oxfordian fossils, between the Fishes and the Cephalopods. 

 We rejoice that the author indexes his Ammonites under this generic 



