No. 4.J HUNO' — ON CAMBRIAN AND SILURIAN. 447 



upon it. The importance of this great Bala group in Britain, 

 and of its North American equivalent, the Matinal of Rogers, — 

 including the whole of the limestones of the Trenton group, with 

 the succeeding Utica and Hudson-River shales, — might justify 

 the invention of a new and special name. That of Cambro- 

 Silurian, at one time proposed by Sedgwick himself, and adopted 

 by Phillips and by Jukes, was subsequently withdrawn by him, 

 when investigations made it clear that this group had been 

 wrongly united with the Silurian by Murchison. Deference to 

 Sedgwick should therefore prevent us from restoring this name, 

 which moreover, from its composition, connects the group rather 

 with the Silurian than the Cambrian. Neither of these objec- 

 tions can be urged against the similarly constructed term of 

 Siluro-Cambrian, which moreover has the advantage that no 

 other new name could possess, of connecting the group both with 

 the true Silurian, to which it has very generally been united, 

 and with the Cambrian, of which, from the first, it has formed 

 a part. I therefore venture to suggest the name of Siluro-Cam- 

 brian, as a convenient synonym for the Upper Cambrian of 

 Sedgwick, (the Lower Silurian of Murchison,) corresponding to 

 the second fauna ; reserving at the same time the name of Cam- 

 brian for the rocks of the first fauna, — the Lower and Middle 

 Cambrian of Sedgwick, — and restricting with him the name of 

 Silurian to the rocks of the third fauna, — the Upper Silurian of 

 Murchison.* 



The late Prof Jukes, it may here be mentioned, in his Manual 

 of Geology, published in 1857, still retained for the Bala group 

 the name of Cambro-Silurian (which had been withdrawn by 

 Sedgwick in 1^54) and reserved the name of the " true Siluriau 

 period " for the Upper Silurian of Murchison. In his recent 



* Dr. Dawson, in his address as president of the Natural History 

 Society of Montreal, in May 1872, has taken the occasion of the 

 publication in the Canadian Naturalist^ of the tirst and second parts 

 of this sketch, to review the subject here discussed. Recognizing the 

 necessity of a reform in the nomenclature of the paleozoic rocks, in 

 conformity with tlie views of Sedgwick, he would restrict to the 

 rocks of the third fauna the name of Silurian, making it a division 

 equivalent to Devonian; and while reserving with Lyell, Phillips and 

 others, the name of Cambrian for the first fauna only, agrees with me 

 in the propriety of adopting the name of Siluro-Cambrian for the 

 second fauna. 



