GRAPTOLITES OF NEW YORK, PART 2 I gg 



which is due to their like composition of man)' tubes. This difference con- 

 sists in the absence of the spines or " scales " forming- so prominent a feature 

 in Inocaulis and Acanthograptus ; the; tubes as a rule emptying directly on 

 the surface of the branches in Palaeodictyota. The difference ma)- also 

 be but one of grade since there are all transitions possible between the 

 highly projecting' bundles of emptying tubes in Acanthograptus and the flat 

 apertures in Palaeodictyota anastoraotica, but it is certain that 

 the combined tendency to anastomosis of branches and the lack of develop- 

 ment of the spines produce a type of structure markedly different from that 

 of the typical Inocaulis. We consider accordingly the combination of these 

 two characters as typical of the genus. 



Professor Whitfield [1902] recognizing from specimens of Ringueberg's 

 species in the American Museum of Natural History the great difference of 

 habitus between that form and the genotype of Inocaulis, has proposed to 

 place I. anastomotic us among the algae J and erected the genus 

 Palaeodictyota (in allusion to the recent alga Dictyota) for its reception. 

 On the supposition that I. anastomoticus is a synonym for I. 

 r a m u 1 o s u s Spencer, the latter is named as genotype of the new genus. 

 I . anastomoticus is, however, as undoubtedly a graptolite as its asso- 

 ciates in the Rochester shale, and distinctly shows in our well preserved 

 specimens the composition of its branches of tubular thecae [see pi. 7, fig. 6]. 

 Further, I. anastomoticus and I. ramulosus are not identical, as 

 the writer had occasion to convince himself by comparison of authentic 

 material 2 and are specifically if not generically different, Spencer's species 

 lacking the frequent anastomoses and possessing fringed margins. It thus 

 happens that Prof. Whitfield cites as genotype I. ramulosus while 



'"The organism is so unlike Inocaulis that I have considered it more natural to place 

 it among the marine algae, but finding no genus of fossil alga that will correspond to it, I 

 have concluded to propose for it the new name Palaeodictyota from its strong similarity 

 to the living form Dictyota Lamereux." 



2 l)r Gurley in his revision of the graptolites from the Niagaran rocks of Hamilton, 

 where both species occur, also distinguishes both forms and compares I. ramulosus 

 with Acanthograptus g r a n t i. 



