374 



THE CAMBRIAN. 



[BULL. 81 



The Solva group of South Wales consists of 150 feet of yellowisl 

 grits beneath 1,500 feet of gray, purple, aud red rocks, above which 15( 

 feet of gray rocks occur. All three divisious are characterized by th< 

 presence of the genus Paradoxides. The superior division of the Mene- 

 vian group consists of 750 feet of slates and sandstones, and, with tin 

 Solva formation, constitutes the Paradoxides zone corresponding to tin 

 Middle Cambrian of the American section. This division is repre- 

 sented in Massachusetts by the Paradoxides beds of Brain tree, in Ne^ 

 Brunswick by the Paradoxides shales of the St. John Basin, and ii 

 Newfoundland by the Paradoxides shales of the Avalon Pcninsul; 

 The faunas of this division are largely identical on the opposite fcidei 

 of the Atlantic, and form the great connecting link that binds tin 

 sections together and permits of almost positive correlation betweei 

 them. 



The North American Upper Cambrian is represented in Wales be 

 the Lingula flags and Lower Tremadoc series, formed of over 5,50( 

 feet of bluish and black slates and flags with bands of gray flags an< 

 sandstones. The faunal and stratigraphic equivalent of this series ha! 

 been distinctly recognized in New Brunswick, on Cape Breton Island, 

 and on the Avalon Peninsula of Newfoundland. 



Most English geologists have included the Tremadoc slates in tin 

 Cambrian ; but from an examination of the list of their contained fating 

 it appears to me that the line of demarcation between the Cambrian 

 and Silurian, if based upon the general facies of the fauna, should b< 

 drawn in the Tremadoc series between the upper and lower division* 

 The fauna of the lower division is essentially that of the Cambrian, 

 with a few genera and species more characteristic of the Lower Silur- 

 ian (Ordovician), while the fauna of the upper division is largely of tin 

 Lower Silurian (Ordovician) type, with a few forms of the Cambrian in- 

 termingled with it. 



The problem of the line of demarcation between the two groups ii 

 England is essentially of the same character as that presented in Ne- 

 vada, where there is no clearly drawn stratigraphic or faunal break ii 

 the Pogonip series of limestones. 



That there is a strongly marked resemblance between the Cambriai 

 series of the Atlantic Coast Province of America and that of tin 

 western Atlantic Coast Province of Wales there is no question. W( 

 are able to compare the three main subdivisions and assume that 

 they belong practically to one province. In fact, there is no more dil 

 ference between the faunas and sediments on the opposite side of tin 

 Atlantic than there is in different portions of the Appalachian Pro- 

 vince, and not as much as between different provinces on the Nortl 

 American Continent. 



In explaining the strong similarity of the faunas and sediments oi 

 the Cambrian rocks of the opposite side of the Atlantic, Dr. Henry 

 Hicks says : 



