1868.] LOGAN— NEW SPECIMENS OF EOZOON. 309 



across several important undulations in the Grenville band 

 in both directions. The Wentworth specimens are imbedded in 

 a portion of the Grenville band which appears to have escaped 

 any great alteration, and is free from serpentine, though a mix- 

 ture of serpentine with white crystalline limestone occurs in the 

 band within a mile of the spot. From this grey limestone, which 

 has somewhat the aspect of a conglomerate, specimens have been 

 obtained resembling some of the figures given by G umbel in his 

 ' Illustrations' of the forms met with by him in the Laurentian 

 rocks of Bavaria. 



In decalcifying by means of a dilute acid some of the specimens 

 from Cote St. Pierre, placed in his hands in 1864-65, Dr. Car- 

 penter found that the action of the acid was arrested at certain 

 portions of the skeleton, presenting a yellowish-brown surface ; and 

 he showed me, two or three weeks ago, that in a specimen recently 

 given him, from the same locality, considerable portions of the 

 general form remained undissolved by such an acid. On partially 

 reducing some of these portions to a powder, however, we imme- 

 diately observed effervescence by the dilute acid ; and strong acid 

 produced it without bruising. There is little doubt that these por- 

 tions of the skeleton are partially replaced by dolomite, as more 

 recent fossils are often known to be, of which there is a noted in- 

 stance in the Trenton limestone of Ottawa. But the circumstance 

 i» alluded to for the purpose of comparing these dolomitized por- 

 tions of the skeleton with the specimens from Burgess, in which 

 the replacement of the septal layers by dolomite appears to be the 

 general condition. In such of these specimens as have been ex- 

 amined the minute structure seems to be wholly, or almost wholly, 

 destroyed ; but it is probable that upon a further investigation of 

 the locality some spots will be found to yield specimens in which 

 the calcareous skeleton still exists unreplaced by dolomite ; a'nd I 

 may safely venture to predict that in such specimens the minute 

 structure, in respect both to canals and tubuli, will be found as 

 well preserved as in any of the specimens from Cote St. Pierre. 



It was the general form on weathered surfaces, and its strong 

 resemblance to Stromatopora, which first attracted my attention to 

 Eozoon ; and the persistence of it in two distinct minerals, pyroxene 

 and loganite, emboldened me, in 1857, to place before the Meeting 

 of the American Association for the Advancement of Science speci- 

 mens of it as probably a Laureutian fossil. After that, the form 

 was found preserved in a third mineral, serpentine ; and in one of 



