XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA. 393 



determined the age of the slates in Georgia, Vermont, holding 

 P. Thompsoni and P. Vermontana." He adds, " at the time I 

 wrote the note on the Highgate fossils it was not known that 

 these slates were conformably interstratified with the Red sand- 

 rock. This discovery was made afterwards by the Rev. J. B. 

 Perry and Dr. G. M. Hall of Swanton." 



Mr. Billings has blamed me (Canadian Naturalist, new series, 

 VI. 318) for having written in 1871 (ante, page 258), with 

 regard to the Georgia trilobites first described as Olenus by 

 Professor Hall, that Barrande "called attention to their pri- 

 mordial character, and thus led to a knowledge of their true 

 stratigraphical horizon." I had always believed that the letter 

 of Barrande and the explicit declaration of Mr. Billings, just 

 quoted, contained the whole truth of the matter. My atten- 

 tion has since been called to a subsequent note by Mr. Billings 

 in May, 1862 (Ibid. (2), XXXIII. 421), in which, while as- 

 serting that Emmons had already assigned to these rocks a 

 greater age than the New York system, he mentions that in 

 sending to Barrande, in the spring of 1860, the report of Pro- 

 fessor Hall on the Georgia fossils, he alluded to their primordial 

 character, and suggested that they might belong to what Mr. 

 Barrande has called " a colony " in the rocks of the second 

 fauna. This is also stated in a note by Sir William Logan in 

 the Preface to the Geology of Canada (page viii). As the 

 genus Olenus, to which Professor Hall had referred the fossils 

 in question, was at that time (1860) well known to belong, 

 both in Great Britain and in Scandinavia, to the primordial 

 fauna, Mr. Barrande does not seem to have thought it neces- 

 sary in his correspondence to refer to the very obvious remark 

 of Mr. Billings. 



Mr. Billings further showed in his paper in March, 1862, 

 that fossils identical with those of the Georgia slates had been 

 found by him in specimens collected by Mr. Richardson of the 

 geological survey of Canada in the summer of 1861, on the 

 Labrador coast, along the Strait of Belleisle ; where Olenellus 

 (Paradoxides) Thompsoni and 0. Vermontana were found with 

 Conocoryphe (Conocephalus) in strata which were by Billings 



