EUROPEAN AUCELLA LOCALITIES. 255 



there was probably no direct connection between the Californian Upper 

 Jurassic deposits and those of the interior. 



M. Neumayr^ has shown the possibility of some of the so-called Lower 

 Cretaceous of British Columbia being Jurassic, and if so, it would be 

 very much higher, that is, Portland. 



Russian Aucella-bearing Rocks. 



Since the confusion as to the age of the Mariposa slates originated 

 from a mistake as to the age of the Aucella-bearing beds of Russia, a 

 few words about these strata may not be out of place. 



The earlier geologists united the j'ounger Mesozoic deposits of Russia 

 under the name " ^Yolga Stage," Avhich most of them thought to be 

 Upper Jurassic, although some ofthem, among whom Eichwald was chief, 

 recognizing Cretaceous affinities in some of the fossils, declared the Wolga 

 stage to be Cretaceous. 



Professor Whiteavesf has gone still further and declared all the 

 Aucella-bearing rocks of Euro2)e and America to be Cretaceous. This 

 view has been emphatically rejected by Neumayr J and Doctor White ;§ 

 but there never was any controversy as to the Jurassic age of the zones 

 of Cardioceras cordatum and of C. cdternans, which were alwa3"S recognized 

 as belonging to the Kelloway-Oxford and Oxford-Kimmeridge respect- 

 ivel3^ In these zones are found several species of AiiceUa. 



The later works || of Pavlow, Nikitin, Lahusen, Michalski and others 

 have shown that the Wolga stage is not a unit, but may be divided into 

 two distinct horizons — the lower Wolga stage, which corresponds to the 

 lower and middle Portland, and the upper Wolga stage, which corre- 

 sponds at the base to upper Portland, and at the top to Neocomian. The 

 correlation of these dei)osits has been materially advanced by the com- 

 parison of the Speeton clays of England with the upper Wolga stage of 

 Russia, by Pavlow^f and Lami)lugh,in which numerous species are cited 

 as being characteristic of the same horizons in the two countries; among 

 these may be mentioned Aucella j^cdlasi, Keyserling, which is said by 

 Nikitin** to be the same as Avicida vellicata, Blake, of the lower Portland 

 or Bolonian stage. 



Doctor White tt admits that Aucella may have been a Jurassic genus 



*Denk. K. Akad. Wiss., Wien, 1885, p. 'JC. 



fGeol. Surv. Canada, 1884, Mesozoic Fossils, vol. i, part i, pp. 2.58-2(Jl, 



I Geojjraph. VeibreitunK Jura, p. 9fi. 



'i Am. Jour. Sei., vol. xxix, 18S5, p. 228. 



II For a resume of the literature of this suVyect, see A. Pavlow, Bull. See. Imper. Nat. Moscow, 

 1889, no. 1, "Jurassique Superieur et Cretace Inf6rieur de la Russie et de la Angleterre." 



^Bull. Soc. Itnp6r. Nat. Moscow, 1891, nos. 3 and 4. 

 ** Bull. Soc. Imp6r. Nat. Moscow. 1889, no. 1, p. 38. 

 ft Monograph xiii, U. S. Geol. Survey, p. 229. 



