GRAPTCL1TES OF NEW YORK; TART 2 [8 







species of the Quebec group, commenting on the similarity of the- grapto- 

 lites of the Quebec and Niagara periods. It is needless to state more than 

 that there is no such resemblance, the disk-bearing forms of the Quebec 

 group being Dichograptidae. In fact no graptolite comparable to this 

 unique fossil — for the genus contains only one 

 species as yet — has been thus far found on this 

 side of the Atlantic and we must turn to Europe, 

 where in Rodonograptus Pocta, Discograptus 

 and Galeograptus Wiman dendroid genera of 

 like habitus have been made known. One or 

 the other of these is likely to be a synonym of 

 Cyclograptusj for they have been erected with- 

 out knowledge of that genus which is not men- s^h^l^^^^yLZwl^V' 

 tioned in their diagnoses. Of Rodonograptus it is stated that it is not 

 sufficiently well preserved to permit a positive decision as to whether there 

 exists "an independent discoidal plate from which the branches proceed or 

 whether this plate has been produced by the compression of the branches 

 which approach each other," the latter being in Pocta' s opinion the more 



probable interpretation, since, " on the best preserved 



^* vfefif jifyhtfc specimens the central disk has no definite contours." 

 jSseN The drawings of Rodonooraptus would seem to support 



aptus would seem to supp( 

 f£> this view. Discooraptus and Galeooraptus, both oenera 

 /fijf im^^ii^a. of Dendroidea from the Borkholmer Schicht in the 

 ^\ <\%\ Baltic region, have distinct disks. We have copied 



here a drawingf of one of each [see text ficr. 8q, qol, since 



Fig. 90 Discograptus & L ° - 7 ' 7 J ' 



homVfLZ iman - (X4) - C ° py these are made from specimens etched out of flint and 

 therefore give a better idea of the original form of the organisms than the 

 compressed shale specimens from our Niagaran and Clinton rocks. It is 

 obvious that both if compressed would give a picture resembling that of 

 our Cyclograptus. The thecae are in both, Galeograptus and Discograp- 

 tus, quite prominent and provided with apertural processes, those of Galeo- 

 graptus having given the genus its name. Our form contrasts with this in 



