GRAPTOLITES OF NEW YORK, PART 1 



599 



with simple branches and dissepiments (consisting of but one series of 

 individuals) and has made a species with compound branches, originally 

 described by him as a Dictyonema (D. tuberosum) the type of a new 

 genus, Reticulograptus. It seems doubtful to me however whether the genus 

 Dictyonema could be properly based on new species without regard to the 

 original genotype, which is a Niagaran form. 



It appears also that gradually the definition of the genus has been 

 extended till it includes forms which can not be considered as falling within 

 the scope of Hall's original definition.  Therefore the subgeneric term Desmo- 

 graptus was proposed by Hopkinson [1875, p.668] in recognition of the fact 

 that in some species the meshes are not formed by parallel branches and 

 straight dissepiments but by the coalescence of the undulating branches. 

 Gurley argues that this group is entitled to full generic rank. As other 

 species (Desmograptus devonicus Gurley and D. intricatus 

 Ruedemann) are clearly proved to possess the same distinctive character, the 

 latter will serve to establish an easily recognized division of the hitherto 

 undivided large genus Dictyonema. 



Hopkinson proposed also [ibid. p.667j the alteration of the name Dictyo- 

 nema into Dictyograptus, on the ground that the former is an old established 

 name for a genus of plants. This proposition has led to an interesting argu- 

 ment between Moberg and Tornquist [1894]. As we see no possible danger 

 of confusion arising by the retention of the old name, we have continued 

 to use it. 



Dictyonema flabelliforme Eichw^ald (sp.) 



Plate 1, figure 1-22 



Gorgonia f labell if ormis Eichwald. Sil. Schicht. Syst. in Esthland. 1840. p 207 

 Gorgonia flabellif ormis Eichwald. Urwelt Russl. H.H. 1842. p.45, tab.l,fig.6 

 Fenestella flabelliformis Eichwald. Beitrage z. Geol. u. Palaeont. Kussl. 



Bui. d. 1. Boc. d. natur. d, Moscou. 1854. no.l, p.6 ; 1855. no.4, p.453 

 Phyllograptasp. Aug. Pal. suec. 1854. p.4 

 Graptopora socialis Salter. Am. Ass'n Proc. 1857. 11:65 

 Dictyonema hisingeri Goppert. Ub. d. foss. Flora d. sil. dev. und nut. 



Kohlenform. etc. 1860. Act. I.eop. 27:31, tab.36,f. 2c, 4-11; tab.45, fig.3, 4 



