■I. I>. Dana — Sedgwick and Mukchisok. 1 7 1 



defined limits. Neither was yet aware of the an fortunate mis- 

 chief-involving fact that the two were overlapping series. 



It is well here to note that the term " Cambrian" antedates 

 •• Taconic" of Emmons by seveii years , ami also that Emmons 



did not know — any more than Sedgwick with regard to the 

 Cambrian — that his system of rocks was in part Lower Silu- 

 rian, and of Llandeilo and Caradoc age. 



In May, of 1S3S, nearly three years later, Sedgwick pre- 

 sented his first detailed memoir on North Wales and the Cam- 

 brian rocks to the Geological Society.* Without referring to the 



characteristic fossils, he divides the rocks below the Old Red 

 Sandstone, beginning below, into (I) the Primary Strati- 

 fied Groups, including gneiss, mica schist and the Skiddaw 

 slates, giving the provisional name of Protozoic for the series 

 Bhonld it prove to be fossiliferous, and (II) the Palaeozoic 

 Series ; the latter including (1) the Lower Cambrian (answer- 

 ing to Middle Cambrian of the paper of 1885), (2) the Upper 

 Cambrian and (3) the Silurian, or the series so called by Mur- 

 chison. Without a report on the fossils, no comparison was pos- 

 sible at that time with Mnrchison's Silurian series. Yet Sedg- 

 wick goes so far as to say that the " Upper Cambrian," which 

 ''commences with the fossiliferous beds of Bala, and includes 

 all the higher portions of the Berwvns and all the slate-rocks 

 of South Wales which are below the Silurian System," " appears 

 to pass by insensible gradation into the lower division of the 

 Upper System (the Caradoc Sandstone);" and that " many of 

 the fossils are identical in species with those of the Silurian 

 System."f Respecting the Silurian System he refers to the 

 abstracts of Mr. Mnrchison's papers and "his forthcoming 

 work." 



The Protozoic division included the " Highlands of Scotland, 

 the crystalline schists of Anglesea and the Southwest Coast of 

 Caernarvonshire." It is added : " The series is generally with- 

 out organic remains ; but should organic remains appear un- 

 equivocally in any part of this class they may be described as 

 the Protozoic System." 



In the later part of the same year, 1838, Murchison's 

 ''Silurian System" was published:}: — a quarto volume of 800 



* An abstract appeared in the Proc. Geol. Soc, ii, 675, 1838. A continuation 

 of the paper appeared in 1841, ibid., iii. 5-11. See also Q J. Geol. Soc, viii, 1852. 



f Of these fossils, he had mentioned " BeUerophon bilobatus, Producta sericea 

 and several species of Orihis " as occurring in the Bala limestone, "all of which 

 are common to the Lower Silurian System," in a Syllabus of his Cambridge lect- 

 ures, published in 1837. 



\ Mnrchison's '• Silurian System " bears on its title page the date 1839. He 

 states in the Q. J. Geol. Soc, viii. 177, 1852. that the work was really issued in 

 1838. The fossil fishes of the volume were described by Agassiz, the trilobites, 

 by Murchisou, and the rest of the species, by Sowerby. 



