GRAPTOLITES OF NEW YORK, PART 2 339 



Suborder B graptoloidea axonophora Freeh 

 Family diplograptidae Lapworth 



DIPLOGRAPTUS McCoy 



The history, astogeny and morphology of thi.s important genus have 

 already been briefly noted in Memoir 7 [p.528, 718]. The structure and 

 development of the rhabdosome have been there set forth according to 

 Wiman's observations and those of the synrhabdosome according to the 

 writer's. In regard to the latter observations, it is, however, to be stated 

 that the growth-stages of the synrhabdosome, which, at the time of their 

 publication, were referred to D. foliaceus, have, together with the 

 form currently here considered as D. prist is Hall (=D . foliaceus 

 Murchison) been since recognized by the writer to represent a variety of 

 D. quadrimucronatus Hall, which in its turn is in this paper placed 

 under Glossograptus. Since the true D. foliaceus forms synrhabdo- 

 somes exactly corresponding to those of G 1 o s s o g r . quadrimucro- 

 natus and other biserial Axonophora (Lasiograptus is here also shown 

 to grow in synrhabdosomes), there can be but little doubt, that the asto- 

 genetic stages of Diplograptus correspond to those of Glossogr. 

 quadrimucronatus published by the writer. 



We figure here a few of a series of fine synrhabdosomes of D . foli- 

 aceus which the Normanskill shale at Glenmont near Albany has afforded 

 and which leave no doubt that the complete colony of that stately Diplo- 

 graptus formed a dense bush of rhabdosomes radiating from a central organ, 

 which however, on account of the density of this branching, could not 

 be discerned. We also, in this connection, refer the reader to the figures 

 of synrhabdosomes of Glossogr. quadrimucronatus and G ? 

 eu char is given under these species. They are camera-enlargements of 

 specimens that were reproduced rather crudely in free-hand drawings by the 

 writer in a former paper on this subject, and show some of the central 

 organs. 



The relation of the first theca to the sicula and its original distal 

 growth direction and later reverse, as well as the budding of the second 



