Prof. T. Sterry Hunt — On Camhrian and Siiun'an. 505 



represent the dawn of organic life. Into the reasons which led 

 Barrande to include the rocks of the first, second and third faunas 

 in one Silurian system (a view which was at once adopted by the 

 British Geological Survey and by Murchison himself), it is not our 

 province to inquire ; but we desire to call attention to the fact that 

 the latter, by his own principles, was bound to reject such a classifi- 

 cation. In his address before the Geological Society in 1842 (already 

 quoted in the first part of this paper), he declared that the discussion 

 as to the value of the term Cambrian involved the question "whether 

 there was any type of fossils in the mass of the Cambrian rocks 

 dififerent from those of the Lower Silurian series. If the appeal to 

 nature should be answered in the negative, then it was clear that the 

 Lower Silurian type must be considered the true base of what I had 

 named the Protozoic rocks ; but if characteristic new forms were 

 discovered, then would the Cambrian rocks, whose place was so 

 well established in the descending series, have also their own fauna, 

 and the Palaeozoic base would necessarily be removed to a lower 

 horizon." 



In the event of no distinct fauna being found in the Cambrian 

 series, it was declared that "the term Cambrian must cease to be 

 used in zoological classification, it being, in that sense, synonymous 

 with Lower Silurian." (Proc. Geol. Soc, vol. iii. p. 641, et seq.) 

 That such had been the result of j)alaeontological inquiry Murchison 

 then proceeded to show. Inasmuch as the only portion of Sedg- 

 wick's Cambrian which was then known to be fossiliferous was 

 really above and not below the Llandeilo rocks, which Murchison 

 had taken for the base of his Lower Silurian, his reasoning with 

 Tegard to the Cambrian nomenclature, based on a false datum, was 

 itself fallacious; and it might have been expected that when the 

 Government Surveyors had shown his stratigraphical error, Mur- 

 chison would have rendered justice to the nomenclature of Sedgwick. 

 But when, still later, a farther "appeal to nature" led to the dis- 

 covery of " characteristic new forms," and established the existence 

 of a " type of fossils in the mass of the Cambrian rocks different 

 from those of the Lower Silurian series," Murchison was bound by 

 his own principles to recognize the name of Cambrian for the great 

 Ffestiniog group, with its primordial fauna, even though Barrande 

 and the Government Surveyors should unite in calling it Primordial 

 Silurian. 



He however chose the opposite course, and now attempted to 

 claim for the Silurian system the whole of the Middle Cambrian or 

 Ffestiniog group of Sedgwick, including the Tremadoc slates and the 

 Lingula-flags. The grounds of this assumption, as set forth in the 

 successive editions of Siluria from 1854 to 1867, and in various 

 memoirs, may be included under three heads: first, that the Lingula- 

 flags have been found to exist in some parts of his orighial Silurian 

 region ; second, that no clearly-defined base had been assigned by 

 him to his so-called system ; and third, that there are no means 

 of drawing a line of demarcation between these Middle Cambrian 

 formations and the overlying Llandeilo. 



