GEOLOGY. 333 



the Cambrian. Inasmuch as the rocks of this infra-Cambrian series in 

 Ontario contain the remains of Eozoon, the Taconian may be desig- 

 nated as Eozoic. The great unfossiliferous Sinisian series of China, and 

 the Vindhyan series of peninsukir India, may perhaps be found to belong 

 to the Taconic horizon, in which connection the association of diamonds 

 with the latter rocks in India, and with the itacolumite in the southern 

 United States is not without signiiicance. 



PALEOZOIC ROCKS. 



The nomenclature of the Lower Paleozoic rocks, from the base of the 

 Cambrian to the top of the Silurian, has long been a matter of discus- 

 tsion. The Cambrian, as originally defined by Sedgwick, extending 

 above the Bala group in Wales, included the Llandovery; from which 

 to the summit of the Ludlow, was the Silurian of Sedgwick (Upper Silu- 

 rian of Murchison), corresponding to the third fauna of Barrande, and 

 including in North America the rocks from the base of the Oneida to the 

 summit of the Lower Helderberg. The Upper Cambrian of Sedgwick, 

 embracing the Arenig, Llandeilo, and Caradoc divisions (the Bala group), 

 which hold the second fauna of Barrande, was from the first claimed by 

 Murchison as a lower member of the Silurian system. Subsequently the 

 Middle Cambrian, including a large part of the first fauna of Barrande, 

 was also claimed under the name of Primordial Silurian, Murchison wish- 

 ing to reserve the name of Cambrian for the lowest division only of the 

 original Cambrian system (the Bangor group of Sedgwick), which other 

 geologists have since attempted to annex to the Silnriau ; thus obliterating 

 the Cambrian from geological nomenclature. While this extreme view 

 has had its advocates, others would maintain entire the Cambrian as 

 originally defined by Sedgwick, and others still have proposed to limit 

 the name of Cambrian to the lower and middle divisions, and to give to 

 the upper division, originally claimed by Murchison as Lower Silurian, 

 the name of Siluro-Cambrian or of Cambro-Silurian. Lapworth has 

 adopted a new solution of the difficulty by giving to the Upper Cam- 

 brian of Sedgwick (Lower Silurian of Murchison) the name of Ordovi- 

 €ian (sometimes contracted by him to Ordoviau), from the Ordovices, 

 a British tribe who, at the time of the Eoman conquet, held North 

 Wales as the Silures did South Wales. The upper limit of the Ordovi- 

 €ian or second fauna is, according to Hicks, the bottom of the Lower 

 Llandovery, and its base the summit of the Lower Tremadoc, the so- 

 called Upper Tremadoc or Arenig being included in the Ordoviciau.* 



In North America the Oneida forms the base of the Silurian, and the 

 Ordovician will embrace the Loraine, Utica, and Trenton (including the 

 Birdseye and Black Eiver) divisions of the New York series. The suc- 

 ceeding Chazy, sometimes absent, perhaps belongs rather to the Ordo- 

 vician than the Cambrian, which latter, as thus limited, will embrace the 



* Geol. Magazine, ii, vi, 1. 



