46 [Assembly 



having the inner side of the branches serrated*. The Dictyonema is 

 known in the Niagara group, the Upper Helderberg limestones, and 

 in the Hamilton group; while the Genus Plumalina, which may be 

 regarded as an allied form, is known in the Chemung group. 



The Graptolitidese are therefore at this time clearly traced to the 

 base of the Carboniferous system, and we may probably find allied 

 genera to the close of the Palseozoic period. 



Various opinions had been entertained, not only as to the nature 

 of the Graptolites, but likewise as to their mode of growth; and it 

 was not until 1854 that the researches in the Geological Survey of 

 Canada brought to light some remarkable and unique forms, which 

 for the first time gave us a true idea regarding their perfect form 

 and manner of growth. 



■Through the kindness of Sir William E. Logan, these specimens 

 were placed in the hands of the writer, and some observations upon 

 them were communicated to him in April 1855 : that notice was 

 soon after read before the Geological Society of France, and other- 

 wise made public in Europe. 



The following extract from the Report of Progress of the Geolo- 

 gical Survey of Canada for 1857 will serve to give a more perfect 

 idea of this discovery, and of the character of the fossils. 



CANADIAN GRAPTOLITES. 



Kepokt of James Hall, Esquire, addressed to Sir William E. Logan, F.E.S., 

 Director of the Geological Survey of Canada. 



Albany, March 1, 1858. 



Sir — In reply to your inquiry regarding the Graptolites and other 

 allied genera, confided to me for description on behalf of the Geo- 

 logical Survey of Canada, partly in 1854 and partly at a subsequent 

 time, I have the honor to inform you that six plates of the Grapto- 

 lites have been engraved, and are now only waiting to be lettered, 

 and that drawings for ten plates more are in the engraver's hands. 



The description of twenty-four species accompanies the present 

 communication, and the plates will follow as fast as they are com- 

 pleted. 



In April 1855, I communicated to you a note upon these remark- 

 able graptolites, discovered in the progress of the Geological Survey 

 during the previous year. This discovery gave for the first time a 



* Mr. Salter was the first to announce publicly the serrate character of these branches, 

 and, not recognizing his fossil as identical with Dictyonejia, proposed the name Grapto- 

 yoEA in 1857. 



