THE HISTOEY OF A DISCOVERY. 00 



from Dr. Dawson by Dr. Carpenter in tlie Journal o£ this 

 Society for August, 1866. 



"In Dr. Dawson's paper mention is made of specimens 

 from Wentworbh, and others from Long Lake. In both of 

 these localities the rock yielding them belongs to the Gren- 

 ville band, which is the uppermost of the three great bands of 

 limestone hitherto described as interstratified in the Lower 

 Laurentian series. That at Long Lake, situated about twenty- 

 five miles north of Cote Sfc. Pierre in the Petite Nation 

 seigniory, where the best of the previous specimens were 

 obtained, is in the direct run of the limestone there : and like 

 it the Long Lake rock is of a serpentinous character. The 

 locaUty in Wentworth occurs on Lake Louisa, about sixteen 

 miles north of east from that of the first Grenville specimens, 

 from which Cote St. Pierre is about the same distance north 

 of west, the lines measuring these distances running 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 

 mixture of serpentine with white crystalline limestone occurs 

 in the band within a mile of the spot. From this grey lime- 

 stone, which has somewhat the aspect of a conglomerate, 

 specimens have been obtained resembling some of the figures 

 given by Giimbel 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. Carpenter 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 immediately observed efiervescence 

 by the dilute acid ; and strong acid produced it without bruis- 

 in<;. There is little doubt that these portions of the skeleton 

 are partially replaced by dolomite, as more recent fossils are 



