432 GRAPTOLITES AND TRILOBITES EROB1 BOLIVIA. [Aug. 1906, 



shows graptolites, but these are rare ; they are preserved as reddish- 

 brown films, and are somewhat distorted. The only form present is 

 a species of Climacograptus, which may be compared with CI. con- 

 fertus, Lapw. If this identification be correct, then the horizon 

 occupied by these pale shales is practically the same as that of the 

 black shales already noticed (namely, Upper Arenig) ; but the 

 evidence, as it stands, is insufficient to settle this point. 



A similar rock obtained from ' the hill-top known as Pilone, 

 between Huanai and Tipuani.' yields an indeterminable fragment 

 of a Dichograptid. 



The specimens have been placed by Dr. Evans in the British 

 Museum (Natural History), South Kensington. 



Discussion (on the two eoregoing Papers). 



The Chairman (Dr. J. E. Mark) asked whether any of the 

 graptolites were found in the beds containing some of the trilo- 

 bites. The Author of one of the papers had stated that the 

 Devonian trilobites were more related to those of South Africa and 

 North America than to those of Northern Europe. He therefore 

 asked whether they bore any resemblance to those of the Devonian 

 beds of Bohemia. 



Dr. J. W. Evans briefly described the localities from which the 

 specimens were obtained. He stated that the differences in 

 characters between the black and the pale Arenig shales appeared 

 to be due to the lateritization of the latter. 



Mr. J. Hopkinson said that the specimens of graptolites' exhibited 

 were very badly preserved, and therefore difficult to determine ; 

 but Didymograptus bifidus, a typical Upper Arenig species, was 

 easily recognizable. Erom the presence of Pliyllograptus he 

 thought that the rocks might extend below the Upper Arenig. The 

 pale shale was very like that found in contact with trap-rocks 

 (greenstone) in the Middle Arenig of St. David's (South Wales), 

 where it contained graptolites, and appeared to be merely the 

 black shale baked. 



Mr. Gr. W. Lampltjgh, commenting on the wide interest of the 

 correlation, remarked that, as the Bokkeveld Beds contained the 

 oldest marine fauna yet discovered in South Africa, no comparison 

 of the South American fossils with the earlier faunas of this region 

 was possible, and the correlation with the European equivalents 

 was therefore necessarily substituted. It was permissible to 

 believe that, if the earlier faunas of the South African region were 

 known, they would show an equally-close agreement with the South 

 American fossils. 



Mr. Philip Lake said that, so far as the trilobites were concerned, 

 the Devonian faunas of South Africa and South America were more 

 closely related to each other than to that of Bohemia. He thought 

 it very likely that, when Cambrian and Ordovician trilobites were 

 discovered in South Africa, they would be found to resemble those 

 of Europe. The differentiation of the Devonian faunas was probably 

 due to a redistribution of land and sea. 



