JURASSIC AND CRETACEOUS 611 



tion described b}^ Halle'^ from Bahia Tekenika, Tierra del Fuego, which 

 is about 60 nautical miles northwest of Cape Horn. It comprises only 

 two generic types {Sphenopteris or Coniopteris and Dictyozamites) , nei- 

 ther of which was sufficiently well preserved to admit of specific determi- 

 nation. It can not have very much weight in the present connection. 



Cretaceous 



Just as it has been found difficult on the basis of available data to dis- 

 tinguish between Triassic and Jurassic, so is it difficult to decide between 

 Jurassic and Cretaceous. Thus, from middle Peru, ISTeumann^^ enumer- 

 ated seven species which he held to be of Wealden age, although they in- 

 clude some apparently Upper Jurassic elements. The same year Lukis 

 mentioned three poorly preserved species of plants from a coal mine near 

 the same locality as those mentioned by Neumann, referring them to the 

 Neocomian. Later, in 1910, Salfeld^^ procured about a dozen species of 

 plants from the same general area, referring them in part to the extreme 

 Upper Jurassic and in part to the lowest Cretaceous. Halle has expressed 

 the opinion that they are probably all to be best regarded as lowest Cre- 

 taceous; also transitional between the Jurassic and Cretaceous, or pos- 

 sibly belonging wholly to the latter, is a small collection described by 

 Halle^^ from Lago San Martin, central Patagonia. It embraces about 

 twelve generic types and a slightly larger number of species. Some are 

 older in affinity as some are somewhat younger, but on the whole Halle 

 concludes that there is nothing to militate seriously against their extreme 

 Lower Cretaceous age. 



One of the most important discoveries bearing on the present discussion 

 was that of an extensive dicotyledonous flora at Cerro Guido, Province 

 of Santa Cruz, Argentina. This flora was listed in a short, unillustrated 

 paper published by Kurtz^^ in 1902. It enumerated 31 forms, of which 

 21, or 75 per cent, are characteristic types of the Dakota group. Although 

 these plants have never been flgured, and it is consequently impossible to 

 check up the identifications, they are mostly such characteristic species 



" T. G. Halle : Kungl. Svenska Vetensk. Handl., vol. 51, 1913, no. 3, pp. 6-12. 



" Richard Neumann : Beltrage zur Kentniss der Ki-eidformatlon in Mittle-Perii. Neues 

 .Talirb., Beilage, vol. 24, 1907, pp. 69-132. 



" H, Salfeld : Fossile Pflanzen aus dem obersten Jura, bzw. der untersten Kreide von 

 Peru. Wissen. ver offenntich. d. gesell. f. Erdkunde, Leipzig, vol. 7, 1911, pp. 211-217. 



"T. G. Halle: Kungl. Svenska Vet.-Akad. Handl., vol. 51, no. 3. 1913. 



15 F. Kurtz : Contribiciones a la palseophytologia Argentina. Sobre la existencia de 

 una Dakota flora en la Patagonia austro-central, Revista Museo La Plata, vol. 10 (1899), 

 1902, pp. 43-60. 



