150 



SCIENCE. 



[N. S. Vol. V. Ko. 108, 



London, 1885, has placed the Wealden forma- 

 tion with Its three groups — Purbeck beds, Hast- 

 ings sand and Weald Clay — into his Oolitic 

 (Jurassic) system. 



This classification of John Phillips was not 

 accepted by the Geological Survey of England 

 and the Director-General, the late Sir Andrew 

 C. Ramsay, in his excellent book, ' The Phys- 

 ical Geology of Great Britain,'' fifth edition, pp. 

 201-212, London, 1878, classifies the ' Purbeck 

 and Wealden strata, ' as Lower Cretaceous, say- 

 ing that the Hastings sands and Weald clay are 

 the fresh-water equivalents in time of the lower 

 and middle part of the Neocomian of Switzer- 

 land; adding, 'an assumption' which 'is un- 

 doubtedly correct.' Such correlation is Inac- 

 ceptable, for -paleontology, lithology and even 

 stratigraphy are wanting entirely, and an ' as- 

 sumption ' cannot replace principles and rules 

 of classification. 



Meantime, the true Neocomian has been found 

 in Yorkshire, northwest of Flamborough Head, 

 near Speeton, and described with details and 

 exact correlations by Prof. J. W. Judd in 1868 

 and 1870, and more recently by Mr. G. W. 

 Lamplugh In 1889 and 1892. Prof. A. P. Pav- 

 low, of the University of Moscow, first in col- 

 laboration with Mr. Lamplugh in 1892, and 

 afterward alone in his paper, On the Classification 

 of the Strata between the Kimmeridgian and 

 Aptian (Quart. Journ. Geol. Soc, London, 

 Vol. 52, pp. 542-554, London, April, 1896), 

 has given correlations of the Wealden with the 

 Speeton clay and Neocomian of western Europe 

 and Russia. Prof. Pavlow places the Purbeck 

 beds in the Jurassic formations and regards 

 them as the equivalent of the Tithonian of south- 

 eastern France. 



Now comes the paper of Prof. O. C. Marsh, 

 first read in 1895 at the British Association at 

 Ipswich, and afterward at the National Academy 

 of Science, New York, meeting November, 

 1896, in which he says that on the vertebrate 

 fauna the Wealden is Jurassic and not Cre- 

 taceoTis. 



Many years ago Louis Agasslz had referred 

 some fossil fishes from the Purbeck of England 

 to species of the upper Jura of Switzerland and 

 France. Lately Mr. Smith Woodward, accord- 

 ng to Prof. Marsh, has found that the fossil 



fishes of the Wealden are of Jurassic types; 

 and finally the paleobotanist, Mr. A. C. 

 Seward, after a review of the Wealden plants, 

 says that the evidence is in favor of ' the inclu- 

 sion of the Wealden rocks in the Jurassic 

 series.' Accordingly, the opinion of Prof. John 

 Phillips, expressed as far back as 1855, is now 

 indorsed by the reptilian fauna, by the fishes 

 and by the fossil plants. Such a concourse of 

 paleontological proofs must correspond with 

 some geographic and stratigraphic facts in the 

 districts of eastern England extending from the 

 island of Portland to Speeton and Filey Bay, in 

 Yorkshire. 



During a prolonged visit at Weymouth, in 

 1870, I was surprised at the small thickness of 

 the Portland stone (only 8 feet) in the cele- 

 brated Portland quarries, and at the great de- 

 velopment of the Purbeck beds covering the 

 whole Island. As far back as 1858 {Sur le- 

 Neocomien dans le Jura, etc., Geneve) I called 

 attention to the correlation of the Purbeck 

 beds with what was called in France ' Calcaires 

 Portlandiens,' or 'Calcaires de Salins' of 

 Franche-Comt6. Since those Portlandian lime- 

 stones of the Jura have been studied with more 

 detail and exactness \\\ regard to their thick- 

 ness and the fossils found in them. It is now 

 certain that they constitute a group of strata 

 all younger than the Portland stone of the isle 

 of Portland. The latter are correlated and 

 identical in every way with the ' Marnes Port- 

 landiennes' or ' Marnes de Salins,' containing 

 exactly the same fauna with its most character- 

 istic fossil, the Exogyra virgula; and we have 

 now an indisputable horizon, common to south- 

 eastern England and France, the Portland stone 

 and the 'Marnes Portlandieunes,' or 'Marnes 

 de Salins,' or zone of the Exogyra virgula. 



In England before reaching the Speeton clay, 

 undoubtedly Neocomian or Lower Cretaceous, 

 we have above the Portland stone, the three 

 groups of the Purbeck beds, the Hastings sand 

 and the Weald clay. In the Jura Mountains, 

 above the ' Marnes de Salins ' with Exogyra 

 virgula, we have the 'Calcaires de Salins,' or 

 Portlandian limestones, composed of two 

 groups ; the inferior called : ' Portlandien In- 

 ferieur,' containing a rich fauna, such as : 

 Nerinea Salinensis, Nerinea yrandis, Natica Mar- 



