496 
PALEONTOLOGY 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 Graptolitidese; 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 b.e 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. Salter was tlie first to announce publicly the serrate character of these branches, and, not re 
cognizing his fossil as identical with Dictyonema, proposed the name Graptofora in 1857. 
