TRIASSIC PERIOD. 443 



to J. D. Hague, there is a deposit of gypsum, two feet thick, on Jarvis 

 Island, overlying the coral sands of the old lagoon, and others 

 similar also on Starbuck's, McKean's, and Phoenix Islands. He 

 attributes the formation of the deposits to the repeated evapor- 

 ation of sea-water, long re-supplied by the tides, over the area of 

 the lagoon, during the time when it was gradually being recovered 

 from the ocean. 



Climate. — There are no data yet obtained for comparing the 

 climate of the Arctic in the Triassic period with that of the Tem- 

 perate United States. 



In the preceding pages, the beds and the period they represent have been 

 called Triassic. Yet it is to be understood that they are probably in part 

 Jurassic. 



2. Foreign. 



The occurrence of ripple-marks throughout most of the European 

 Triassic sandstones and marls, and also raindrop-impressions and 

 cracks from drying, show that the beds are of shallow-water and 

 mud-flat origin ; and the salt — as explained on p. 249 — indicates 

 that there were flats exposed to occasional inundations of the sea, 

 where the salt water evaporated. The kinds of rock are similar to 

 those of the Saliferous region in central New York, although they 

 belong to very different periods : the history of one is probably 

 essentially that of the other. 



The fossiliferous limestone (Muschelkalk) of the Middle Trias 

 in Germany indicates that in that region there -was for a while an 

 interval of somewhat deeper waters. 



As the alternations in these beds depend on small changes 

 of level over limited areas, there is sufficient reason for their not 

 occurring in other regions. 



Appendix. — In Asia and Australia there are coal beds of considerable extent, 

 which have been referred to different periods from the Carboniferous to the 

 Jurassic. The Asiatic deposits occur at Burdwan in western Bengal, where they 

 are extensively worked, and about Nagpur in the Deccan, India. In Australia 

 they cover a large surface in New South Wales, extending inland from the 

 coast. 



The fossil plants of the first region are species of Pecojrteris, Glossopteris (an 

 oblong simple-leaved fern). Tzeniopteris. Vertebraria (stems of unknown rela- 

 tions), Phytlotheca (of the Equisetum tribe), Zamites, etc. About Nagpur nearly 

 the same genera and partly the same species occur, excepting the Cycads. In 

 the Australian beds there is a similar resemblance to the Burdwan coal field. 



On account of the absence of the peculiarly Carboniferous genera in both 

 the Asiatic and Australian beds, and the general similarity of their flora, while 



