GRAPTOLITE ZONES 275 



Similar facts have been afforded by the study of the 

 Cretaceous strata ; and even the complicated lower 

 Palaeozoic sediments, yielding to the genius of Lapworth, 

 have been reduced to a regular succession of zones, which, 

 so far as our knowledge extends, follow one another in 

 the same order wherever they are visible in the northern 

 hemisphere. 



The fossils which Lapworth made use of as a means of 

 identification are the Graptolites, small and frequently 

 obscure forms, which depend on minute observation for 

 their specific distinction, and not likely at first sight to 

 recommend themselves as the most promising of guides : 

 but by their means it has been found possible to unravel 

 the amazing intricacy of the southern Uplands of Scotland, 

 a district which, on account of its complications, had 

 resisted all previous efforts to reduce it to order. Messrs. 

 Marr and Nicholson have extended Lapworth's classifica- 

 tion to the lake district of Cumberland and Westmoreland : 

 it has been shown to obtain in Wales, France, Spain, 

 Bohemia, Thuringia, Scandinavia, and North America. In 

 the southern hemisphere, beds have been observed con- 

 taining the same Graptolites as occur in the Ordovician 

 system of the northern hemisphere, but in this case the 

 succession is by no means so clear. In New Zealand it 

 has not yet been studied. In Australia,* Mr. T. S. Hall 

 thinks he has discovered a divergence from Lapworth's 

 succession, but the facts are somewhat doubtful. Some of 

 the genera extend through longer intervals than in our 

 hemisphere, but this, as Waagen has pointed out, is by no 

 means inconsistent with zonal identity, which depends 

 on identity of species, and these, as Mr. Hall admits, 

 may not have been rightly determined in the case of the 

 Australian specimens (loc. cit., p. 177). We must there- 



* T. S. Hall, " Presidential Address to Section C. Australasian 

 Assoc. for the Adv, of Science," 1900, p. 176. 



