GRAPTOLITES OF NEW YORK, PART 2 



379 



the oblique breaking' of the shale through a point of the spine where it was 

 slightly bent sidewise, the combined oblique fracture and sidewise bending 

 producing a wider, club-shaped section of the spine. Since; in G . c i 1 i- 

 a t u s unit, h o r r i d u s only a fraction of the spines of a few rhabdosomes 

 are bulbous, the)' can not be considered as constituting a specific charac- 

 ter. Furthermore, they are shorter than the other spines and obviously 

 incomplete. There has further in no other species of Glossograptus 

 been observed anything pointing to a tendency of jointing or segmentation 

 of the spines, while it is easily conceived that the fine, more or less parallel 

 fractures, which transect all graptolites in shale, could properly directed, 

 give the spines a jointed appearance. But with the explanation of the 

 above-mentioned peculiarities of this species as freaks of preservation, there 

 is nothing left to distinguish it by and it becomes more than probable that 

 it is another synonym of G . ciliatus. 



In G . arthracanthus, as well as in G . setaceus the spines are 

 straight and could therefore be thought to be distinguished by this char- 

 acter from the reflexed spines of G. ciliatus. But they are clearly 

 incompletely preserved in the type specimens of both species and corre- 

 spond only to the straight proximal parts of the thecal spines or to the 

 straight spines of the median line of the lateral faces. 



For reasons given in their descriptions and on p. 85 we have also 

 referred Diplograptus quadrimucronatus and D. whitfieldi 

 to this genus. The former has been made by Lapworth the type of a new 

 subgenus ( Orthograptus) which, then, may also become available as a 

 subdivision of Glossograptus. 



Glossograptus ciliatus Emmons 



Plate 26, figures 1-5; plate 27, figures 1-4 



Glossograptus ciliatus Emmons. Am. Geol. pt 2. 1856. p. 108; pi. 1, fig. 25 

 Glossograptus setaceus Emmons. Ibid. p. 236 ; pi. 1, fig. 20 

 Graptolithus spinulosus Hall. Pal. N. Y.. 1859. 3:507 (fig.) 

 Graptolithus spinulosus Hall. N. Y. State Cab. Nat. Hist. 13th An. Rep't 

 i860, p. 60 



