Reviews — Dr. A. Bigot — Archcean and Cambrian of France. 181 



gonangium. Dr. Holm further describes and figures some remarkably 

 "well-preserved examples of Eetiolites and Stomntograptus, in which 

 the structural details are clearly shown. 



In the third paper, Professor Tornquist describes 22 species of 

 Graptolites occurring in the Ordovician and Silurian strata of the 

 district of Siljan ; of these the following are regarded as new, 

 Clonograptus robiistus, Tetragraptus curvatus, Didymograptus gracilis, 

 D. deceits, Climacograptus internexus, and Diplograptus hellulus. 

 Many of the species in the area referred to are likewise common to 

 the Coniston Flags and to the Quebec Group of Canada. 



E, E "V IIE "Vv^ S. 



L'Akcheen et le Cambkien dans le Nord du Massif Breton 



ET LEURS EQUIVALENTS DANS LE PaYS DB GalLES. Par A. BiGOT, 



Docteur-es-Sciences. (Cherbourg, 1890.) 



DOCTOE BIGOT is a young French geologist who is rapidly 

 winning his spurs. Having done excellent work amongst the 

 older rocks of Northern France, he came over to Great Britain, and 

 compared the systems with which he was familiar with some of the 

 basal rock-groups of Wales and Shropshire. The results of this 

 comparison are given in the work before us, and will be found to be 

 in substantial agreement with the views maintained by those who 

 in this country have paid the fullest attention to the Arch£ean and 

 Cambrian rocks. 



In the first part of his work Dr. Bigot describes the phyllads and 

 purple conglomerates in the district of Saint-Lo and in the west of 

 Calvados, From the typical area, he passes to the northern extension 

 of these formations, as studied in the district round Cherboui-g. He 

 then takes up the same rock-groups south of Saint-Lo, and describes 

 their occurrence in the south of Calvados, at Granville, and in the 

 island of Jersey, which lies about 30 miles to the north-west of 

 Granville. In Chapter IV. the author discusses the relation between 

 the Phyllads and the older Paleeozoic groups. Chapter V. gives an 

 account of the eruptive rocks of Normandy and the Channel Isles ; 

 and Chapter VI. concludes the first part with a description of the 

 general stratigraphy of the Breton massif. In the succeeding chapters 

 the author discusses the correlations of the older rocks of north- 

 western France with their equivalents in Pembrokeshire, North 

 Wales, and Shropshire ; and winds up with an excellent summary 

 of his conclusions. Then follows a valuable bibliographic index, 

 the authors being classed under the respective heads of " The Breton 

 massif," and" Wales" (including Shropshire). 



The schistose and slaty rocks named after the town of Saint-L6, 

 and usually referred to by French geologists as " schistes " or 

 " phyllades," have been described by a long series of writers. 

 Dufrenoy in 1838 identified them with the Cambrian of Great 

 Britain, a very natural opinion at a time when the Longmynd 

 series was accepted as typical Cambrian, and when the existence 

 of slaty rocks below the Cambrian was not recognized in Europe. 



