DEVONIAN AND OLD RED SANDSTONE SYSTEM 243 



dry and desert conditions prevailed over the central parts of the 

 incut, including the British region; that the lakes shrank to 

 small proportions, if they were not entirely dried up. On this 

 supposition the change which took place may have been a return to 

 more humid conditions, an increase in the rainfall, especially on the 

 mountain ranges, resulting in the birth of torrential streams at 

 certain seasons, which swept out the stones and pebbles that had 

 accumulated in the higher valleys and spread them out on the 

 desert plains, for there is sufficient evidence that the Caledonian 

 area at any rate was such a desert plain. 



As the annual rainfall increased, lakes were once more formed, 

 and were again peopled with fish, but new kinds of fish had in the 

 meantime been developed in the surrounding sea, so that the fish 

 of the Upper Devonian lakes were a very different assemblage 

 from that which lived in the older lakes. Finally we have 

 evidence of a slow subsidence of the whole region and of the 

 invasion of these lakes by the waters of a Carboniferous Sea. 



REFERENCES 



1 Jukes, Quart. Journ. Geol. Soc. vol. xxii. p. 320 (1866). 



2 Etheridge, Quart. Journ. Geol. Soc. vol. xxiii. p. 568 (1867). 



3 Hicks and Whidborne, Quart. Journ. Geol. Soc. vol. Hi. p. 254, and 

 liii. p. 438. 



4 W. A. E. Ussher, Quart. Journ. Geol. Soc. vol. xlvi. p. 487 (1890). 

 8 See E. Hull in Quart. Journ. Geol. Soc. vol. xxxv. p. 703 (1879). 



8 See Jukes, Quart. Journ. Geol. Soc. vol. xxii. p. 340, and Explanations 

 of sheets of the Geol. Survey Maps of Ireland. 



7 See paper by Prof. Hull (above cited). 



8 Geology of the Country around Cork, 2nd ed. (1905). 



9 See Heer in Quart. Journ. Geol. Soc. vol. xxviii. p. 163 (1872). 



10 C. Barrois, Proc. Geol. Assoc. vol. xvi. p. 101 (1899). 



11 .Ehlert in Bull. Soc. Geol., France, for 1889, p. 742; and " Livret- 

 Guide de 1'Excursion en M avenue," Geol. Congres Internal. , 1900. 



12 C. Barrois, "Terr, auciens des Asturies," Mem. Soc. Gfol. Jford, 1882. 



13 J. Gosselet, Proc. Geol. Assoc. vol. ix. p. 228. 



14 See Kiiyser, Zeitsch. deutsdi. geol. Ges., Bd. xxxiii. p. 617 (1881) ; and 

 Koch, Jahrb. k. preuss. geol. Landesanst. xx. p. 237 (1900). 



13 F. Seemanu, Beitr. Paldont. Oesterr.-Ung. xx. p. 69-114 (1907). 

 1B " Geology of West Gower," Mem. Geol. Survey (1907). 



17 G. Hickling, Geol. May. for 1908, p. 396. 



18 J. G. Goodchild, Proc. Geol. Assoc. vol. xviii. p. 117. 



19 Sum. Prog. Geol. Survey for 1898, p. 87 (with map). 



20 J. Nolan in Quart . Jnvrn. Geol. Soc. vol. xxxvi. p. 529 (1880). 



Kayser in Stockholm Vet. Ak. Bch. Bd. xxvii. (1901) ; Nathorst in 

 Bull. Soc. Instil. Upsala, voL x. (1910) ; and A. S. Woodward in Ann. 

 Mag. .W. ///.< s. 6, vol. viii. (1895). 



22 See Heer in Quart. Journ. Geol. Soc. vol. xxviii. p. 163. 



