walcott.] IRELAND CHINA. 377 



IRELAND. 



The supposed representative of the Welch Cambrian series in the 

 southeast of Ireland is described by Prof. Geikie as follows : 



In the southeast of Ireland, masses of purplish, red, and green shales, slates, grits, 

 quartzites, and schists occupy a considerable area and attain a depth of 14,000 feet 

 without revealing their base, while their top is covered by unconformable formations 

 (Lower Silurian and Lower Carboniferous). They have yielded Oldhamia, also numer- 

 ous burrows and trails of annelides (Hlstioderma hibernicum, Arenicolites didymus, A. 

 sparsus, Haughtonia pcecila.) No Upper Cambrian forms have been met with in the 

 Irish rocks, which are therefore placed with the Lower Cambrian, the unconforma- 

 bility at their top being regarded as equivalent to the interval required for the depo- 

 sition of the intervening formations up to the time of the Llandeilo rocks, as in the 

 .northwest of Scotland. 1 



A very full description of the Cambrian rocks of Ireland, especially 

 as they occur at Bray Head, Wicklow, is given by Prof. William Hellier 

 Baily in 1865. A diagrammatic section accompanies the paper, and the 

 author also describes the supposed organic remains that have been 

 found in the rocks. 2 



CHINA. 



Our knowledge of the Cambrian rocks of China results from the 

 investigations of Baron Richthofen in the province of Liau-tung in north- 

 eastern China, near the Corean frontier. He found a series of lime- 

 stone containing the "Primordial w fauna in the sections of Sai-maki 

 and Tai-tsze ho. 3 The limestones are superjacent to a series of sand- 

 stones and quartzites that correspond in stratigraphic position to the 

 Lower Cambrian of North America. 



The collections of fossils were studied by Dr. Wilhelm Dames, who 

 came to the conclusion that two horizons were represented — the Au- 

 drarum limestone or Paradoxides horizon of Sweden, and the Quebec 

 horizon of North America. 4 At the time Dr. Dames wrote Dikeloeeph- 

 alus gothicus and D. quadriceps, which he referred to the genus Dor- 

 opyge, were cited as from the Quebec group ; and it was on the com- 

 parison between the Doropyge richthofeni and these two species that he 

 considered that the Quebec horizon was represented. The two species 

 mentioned are now referred to the genus Olenoides of the Middle Cam- 

 brian fauna, which is not known to occur in the Upper Cambrian or in 

 the Calciferous-Chazy fauna corresponding to the Quebec. A study of 

 the species illustrated by Dr. Dames leads me to think that the Middle 

 Cambrian fauna only is present, although it is not impossible that 

 some Upper Cambrian species may have been collected. The sections 

 of Baron liichthofen, however, indicate a considerable thickness of con- 



1 Text Book of Geology, 1885, p. 654. 



2 The Cambrian rocks of the British Islands, with especial reference to the occurrence of this forma- 

 tion and its fossils in Ireland. Geological Magazine, vol. 2, 1865, pp. 385-400. 



3 Richthofen, F. F. von: China. Ergebuisse eigener Reisen und darauf ge^rundeter Studien. Vol.2 

 (das nordbche China) fig. 21, p. 94; fig. 29, p. 101, 1882. 

 4 Cambrische Tiilobiten von Liau-tung. China ; by F. F. von Richthofen, vol. 4, 1883, p. 33. 



