278 C. SCHUCHERT MORRISON AND TENDAGURU FORMATIONS 



as Lower Kimmeridge, and the lower dinosaur beds as lowest Oxford or 

 even Kellowa}^ 



Dietrich*^ has studied all the gastropods of the Tendaguru series and 

 has named thirty-six species, either specifically or generically, of which 

 only seven were previously known forms. On the basis of these fossils he 

 concludes that the Trigonia schwarzi zone indicates Tithonian to middle 

 Keocomian, the T. smeei zone equals Kimmeridgian, and the jSTerinea zone 

 equals middle Dogger to Kimmeridgian. 



"The gastropods of the Tendaguru series from the base up to the upper 

 dinosaur zone give one a fairly clear impression that it is a shallow-water 

 assemblage of Kimmeridgian age, and that it is independent of the higher 

 faunas that are of Lower Cretaceous time. In regard to the age of the Nerinea 

 and basal beds the correlation is uncertain," 



Lange/^ on the basis of the bivalves, makes the following correlation: 



Zone with Trigonia schwartzi, T. transitoria, and T. conocardiiformis = Middle 



Neocomiau. 

 Upper dinosaur zone = Lower Neocomian. 

 Zone with Trigonia smeei and T. venM<?os(i = Uppermost Jurassic. 



Conclusions hy Buckman. — As the geologic age of the Tendaguru series 

 is largely based on the inherent evidence of the ammonites, the writer 

 asked his friend, Dr. S. S. Buckman, the English authority on Middle 

 Mesozoic ammonites and stratigraphy, to read the work of Zwierzycki 

 with a view of endorsing or emending his age determinations and corre- 

 lations. This Buckman has done, and, as will be seen from his state- 

 ments, there is no essential disagreement. Under date of November 8, 

 1916, Doctor Buckman writes me as follows: 



"With regard to the Tendaguru series there seems no reason to take excep- 

 tion to Zwierzycki' s general conclusion — that the series ranges in date from 

 Jurassic to Neocomian. The Trigonia schwarzi beds are Neocomian, the T. 

 smeei beds are Jurassic. He says that the Ammonites of the latter indicate a 

 mixed fauna; the highest, Craspedites, would indicate Purbeckian — infra- 

 Neocomian at any rate: some others are Kimmeridgian forms, as he points 

 out: to these may I think be added his P. J)leicherl. of which the identification 

 seems doubtful — it has greater likeness to one of oui- Upper Kimmeridgian 

 species : the author cites it as evidence for Portlandian. 



"In the Nerinea beds P. sparsipUcatiis, of which the identification is much 

 to be questioned, suggests more nearly another of our Upper Kimmeridge 

 forms, while P. cf. achilles would be about border-line of Kimmeridgian- 

 Argovian. 



"The Tendaguru series thus appears to be a straddle formation from the 



*5 W. O. Dietrich : Op. cit., part ili, pp. 109-110. 

 « E. Lange : Op. cit., part iii, p. 289. 



