94 GEOLOGY. 



The geographical conception suggested by the distribution of the Aucella 

 is perhaps strengthened somewhat by the occurrence of corals in the California 

 province, and their absence from the Dakota province. Neumayr has shown 

 that corals were essentially absent from the northern Russian province, while 

 they abounded in the central and southern European provinces. From this 

 more southerly habitat, their distribution to the Indian province and thence 

 to California, would be consistent with their absence from the Dakota province, 

 if the route along the Pacific sea-shelf were isolated from the Dakota province, 

 as suggested. At the same time, it is not impossible that the former continental 

 tract which connected Asia with Australia and New Zealand, of which there is 

 abundant evidence, may have been extended so as to connect with South America 

 by way of the Antarctic land, from which Australia and South America are 

 separated, respectively, by moderate distances only, and by sea-depths about one 

 third the usual abysmal depths. This would best harmonize with the distribu- 

 tion of the Arietidce from Europe to Timor on the line of the old continental 

 extension between Java and Australia, and thence to the Argentine Republic 

 and to California, where Hyatt finds evidence of their progressive advance from 

 the south to the north. But these suggestions must be held lightly until sup- 

 ported by more evidence. 



The Land Life. 

 I. The vegetation. 



The land vegetation of the Jurassic was little more than a con- 

 tinuance and enrichment of that of the late Triassic, with slow prog- 

 ress toward living types, cycadeans, conifers, ferns, and equiseta 

 being still the leading forms, slightly more modernized, but not radi- 

 cally changed. 1 The cycadeans (Bennettitales and Cycadales) were 

 perhaps the most distinctive forms, constituting this the climax of 

 the " age of cycads," but the conifers showed the more notable moderni- 

 zation. They embraced yews, cypresses, arborvitas, and pines, all 

 of which assumed a somewhat familiar aspect, though the species 

 were all ancestral. The ginkgos also played a somewhat important 

 role. 



An interesting feature of the European record is the rather fre- 

 quent occurrence of land plants in marine beds, which not only implies 

 that many trunks, twigs, leaves, and fruit were floated out to sea, but 

 that the landward edges of the deposits escaped serious erosion, a 



1 For a comprehensive paper on the Jurassic plants of the United States, with 

 descriptions and illustrations by Lester F. Ward, see 20th Ann. Rept. U. S. Geol. 

 Surv., 1898-99, pp. 334-430. 



