300 THE CANADIAN NATURALIST, [Vol. \i, 



led liim to propose several sub-divisions. Thus he distinguished 

 on paleontological grounds between the upper and lower Tremadoo 

 slates, and for like reasons divided the Lingula-flags into a lower 

 and an upper portion. For the discussion of these distinctions 

 the reader is referred to the memoirs of the Geol. Survey [III, 

 240-257.] Subsequent researches led to the division of the ori- 

 ginal Lingula-flags into three parts, an upper and a middle, to 

 which the names of Dolgelly and Maentwrog were given by Mr. 

 Belt, and a third consisting of the basal beds, which .were se- 

 parated in 1865, by Salter and Hicks, with the designation of 

 Menevian, derived from the ancient Roman name of St. David's 

 in Pembrokeshire. It was here that in 1862, Salter found 

 Paradnxides with Agnostus and Lingula in fine black shales at 

 the base of the Lingula-flags, resting comformably on the green 

 and purple grits of the Lower Cambrian or Harlech beds. The 

 locality was afterwards carefully studied by Hicks, and it was 

 soon made apparent that the genus Paradoxides, both here and in 

 North Wales, was confined to a horizon below the great mass of 

 the Lingula-fligs ; which, on the contrary, are characterized by 

 numerous species of Olenus. These lower or Menevian beds are 

 hence regarded by Salter as equivalent to the lowest portion of 

 the Eta2;e C of Barrande. 



Beneath these Menevian beds there lies, in apparent conformity, 

 the great Lower Cambrian series, frequently called the bottom 

 or basement rocks by the Government surveyors ; represented 

 in North Wales by the Harlech grits, and in South Wales, near 

 St. Davids, by a similar series of green and purple sandstones, 

 considered by Murchison, and by others, as the equivalent of the 

 Harlech rocks. They were still supposed to be unfossiliferous 

 until in June, 1867, Salter and Hicks announced the discovery in 

 the red beds of this lower series, at St. Davids, of a Lingulella, 

 very like L.ferruginea of the Menevian. [Geol. Jour. XXIII, 

 339 ; Siluria 4th ed. 550.] This led to a farther examination 

 of these Lower Cambrian beds, which has resulted in the dis- 

 covery in them of a fauna distinctly primordial in type, and 

 linked by the presence of several identical fossils to the Menevian ; 

 but in many respects distinct, and marking a lower fossiliferous 

 horizon than anything known in Bohemia or in Scandinavia. 



The first announcement of these important results was ra ide 

 to the British Association at Norwich in 1868. Further details 

 were, however, laid before the Geolo2ical Society in May, 1871, 



