304 



JDB. L. F. SFATH ON 



[vol. Ixxix, 



that Dr. W. Kilian, 1 the authority on the French succession, on the 

 one hand records Berriasella privasensis as still occurring in 

 the Cretaceous, and, on the other, claims the Valanginian genus 

 Thar ma unites also from the Tithonian or uppermost Jurassic. 



Prof. Emile Haug 2 includes the ' Purbecldan ' in the Portlandian 

 as its upper, non-marine, portion, bat it seems preferable to retain 

 Oppel's term Tithonian ; for, although it has been misapplied to 

 beds the Kimmeridgian age of which was not recognized at the 

 time, Oppel clearly meant it to be used for strata that are transi- 

 tional to, or indicate the dawn of, the Cretaceous. 3 



Recent researches indicate that there is room for a very long 

 and important epoch between the Cretaceous and the Portlandian, 

 an epoch for the widely-scattered marine equivalents of which the 

 terms ' Purbecldan ' or 'Aquilonian' seem inappropriate. Haug's 4 

 opinion of the equivalence of the Tithonian, Portlandian, and 

 Volgian cannot now be upheld, and from the appended table it 

 will be seen that, with the Lower Tithonian below, the}' are here 

 considered to represent four successive periods. 



Suggested Sequence of Ammonite Zones in the Upper Jueassic. 



Zones. 



r 



privasensis. 



Tithonian. < 



pronus. 



coutiguics. 



U 



l giganteus. 

 Portlandian. ypseudogigas. 

 Igorei. 



rTT ( ' paUasianus. 



[Upper. \ r 



Vvirgatus. 



{ steraspis. 



H Middle. 



<J gigas. 

 [^eudoxus. 



[h ower. ] tenvilobatus. 



Subzones. 

 ( occitanica. 

 -j mendozana. 

 (. behrendsoni. 

 C tentii striata. 

 < densestriatus. 

 (_ idoceroides. 

 ( eiidicJwtomiis. 

 ( chalmasi. 



rotundus. 



pectinatus. 



blalcei. 



virgatus. 



' miatchJcoviensis.' 



danubiensis. 



vimineus. 



ulmensis. 



bleicheri. 



zio. 



comatus. 



pseiidopolitula. 



subeumela. 



yve-grauesi. 



phorcus. 



eudoxus. 



pseudomutabilis. 



ba hlerus. 



mutabilis. 



polyplocus. 



platynota. 



planulus. 



' Lower Berriasian or 

 Purbeckian.' 



Y ' Volgian.' 



1 



' Lower Tithonian ' 

 (' acanthicus zone '). 



1 Op. cit. (' Lethsea Geognostica ' fasc. 2, 1910) pp. 171-82. 

 - ' Traite de Geologie ' vol. ii, fasc. 2 (1907) p. 1075. 

 :i Tithon was the spouse of Eos (Aurora), the goddess of dawn. 

 4 ' Portlandien, Tithonique & Volgien ' Bull. Soc. Geol. France, ser. 

 vol. xxvi (1898) pp. 197-228. 



