1^0. 1.] ANNUAL ADDRESS. 7 



logy," the second edition of wliicli was then in the press. But 

 Sir Roderick was naturally umvilling to change the boundaries 

 of that Sikiria which he had conquered and over which he had 

 reigned, and I contented myself at the time with affirming that 

 the Silurian system, as held by Sir Roderick, really consists of 

 two groups, which should have distinct names ; but the question 

 of the names I left to others. Dr. Hunt has now the credit of 

 raising the question in a practical form, and I agree with him 

 that the term Silurian sliould be restricted to the Upper Silu- 

 rian of Sir Roderick, which constitutes a distinct period of the 

 earth's history, equivalent to the Devonian or the Carboniferous. 

 The Lower Silurian is really another distinct group, but to 

 avoid multiplication of names, and as it formed the battle-ground 

 of the Silurian and Cambrian controversy. I concur in the 

 view that it may well have the name Siluro-Camhrian , while 

 the name Cambrian or Primordial will remain for those great 

 -and important fossil ifero us deposits extending downward from 

 the Potsdam in America and the Tremadoc in England, and 

 constituting an imperishable monument to the labours of Sedg- 

 wick and Barrande. 



There remains one point still before leaving this subject. It 

 is the gap between the fauna of the Primordial and that of the 

 Laurentian — the latter still represented only by that Titan of for- 

 aminifers, Eozbon Ccmadcnse. Barrande refers to this gap in his 

 memoir above mentioned ; and I had hoped ere this time to have 

 done something to bridge it over. I may here state in antici- 

 pation of the results of researches still incomplete, (1) That in 

 rocks of Huronian age in Bavaria and probably also in Onta- 

 rio. Eozoon has been found. (2) In the middle and Upper 

 Cambrian we know as yet few limestones likely to contain .such a 

 fossil, but we have in Labrador species of Ai-cJiceoci/athus, one of 

 which I have ascertained to be a calcareous chambered organism 

 of the nature of a foraminifer; though there seems little doubt 

 that others are, as Mr. Billings has shown, allied to sponges. 

 (3) In the Cambro-Silurian, in the limestones of the Trenton 

 group, animals of the type of Eozoon return in full force. The 

 concentrically laminated fossils which sometimes form large 

 masses in these limestones, and which are known as Stroma topor a, 

 are mostly of this nature, though it is true that fossils of the 

 nature of corals have been included with them. In the Silurian 

 proper, we have the similar if not identical forms known as 



