336 Correlation of the Upper Cretaceous Formations 



Europe than it is in this country, yet it is peculiarly characteristic of 

 the Emscher. The Delaware species, Mortoniceras delawarensis, has heen 

 reported in a number of the European check-lists from the lower Cam- 

 panian, but the European form differs from the American in the regular 

 bifurcation of the costaa and probably is at most a descendant of the 

 American species. Baculites asper is common to both the Mortoniceras 

 subzone and the Emscher, but it has been reported from the Santonian of 

 Westphalia as well as from the Coniacian. Placenticeras placenta has 

 also been reported from the Emscher, but the determination is by no 

 means certain. The Niobrara fauna contains in the Inocerami additional 

 criteria for correlating widely separated faunas. Out of the four species 

 listed from the Niobrara, two, Inoceramus umbonatus and I. exogyroicles, 

 are considered specifically identical with forms restricted to the Emscher. 

 Both of the Inocerami in question occur in the Austin chalk, but they 

 have not been recognized from any other horizon. Gryphcea vesicu- 

 laris, a species rare in the Mortoniceras subzone, is widely distributed 

 through the upper part of the Upper Cretaceous, but it has never been 

 recognized in strata older than the Emscher ; in fact, in the opinion of the 

 junior author, none of the species of the Mortoniceras subzone has been 

 identified from as early a horizon as the Turonian, nor do any of them 

 show any marked affinities to faunas contained in strata of that age. 



The most striking feature of the European Upper Cretaceous faunas is 

 the dissimilarity between the northern and the southern. The northern 

 fauna has been recognized in England, northern France, Germany, Russia 

 and Scandinavia ; the southern throughout the Mediterranean province. 

 This segregation holds good not only for the European continent but also 

 in the Asiatic, African and North American regions. 



The northern faunas are characterized by the abundant presence of 

 Aucella, Polyptycliites and Cylindroteutliis in the Lower Cretaceous, and 

 Inoceramus, Actinocamax and Belemnitella in the Upper, and by the 

 comparative or complete absence of the Diceratids, the Rudistids and the 

 reef corals. 



The southern fauna is characterized by the abundance of the reef- 

 building corals and of Orbitolina, the Diceratids, Phylloceras, Leptoceras, 



