496 PALiEOiNTOLOGY OF NEW-YORK. 



In a short paper published in the Proceedings of the American As- 

 sociation for the Advancement of Science for 1849, I stated that the 

 Graptolites were not represented in the higher Silurian, Devonian or 

 Carboniferous strata. Subsequently, however, in the same year, I deter- 

 mined the Genus Dictyonema to belong to the Graptolitideoe ; and this 

 opinion was expressed in the second volume of the Palaeontology of 

 New- York in 1850 (though the volume was not published till 1852). The 

 Dictyonema, on farther examination, has proved to be an unequivocal 

 graptolitic genus, consisting of radiating filaments or branches which are 

 connected together by transverse bars, and form flabellate or funnelshaped 

 fronds growing from a radix, and 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 Graptolitideae 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 Palaeozoic 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 1855 : that notice was soon after read before 

 the Geological Society of France, and otherwise made public in Europe. 



The following extract from the Report of Progress of the Geological 

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

 discovery, and of the character of the fossils. 



* Mr. Saltib wag the first to announce publicly the serrate character of these branches, and, not re- 

 cognizing his TussU as Identical with Dicttoncma, proposed the name GRAPTorosA in 1857. 



