472 NEW YORK STATE MUSEUM 



111 America the work on tlie graptolites has rested for a long time, partly 

 on account of the unpromising character of the graptolitiferous rocks and partly 

 because the many new fields of investigation offered by a large continent, 

 completely held the attention of the small band of paleontologists. Lapwortli 

 [1886], however, demonstrated the general parallelism of the succession 

 of the faunas of Canada and Great Britain ; Mattheio [1891, 1895] brought out 

 some important facts incidental to his investigations in the St John basin ; and 

 Ami [1888] has published lists of graptolites from numerous outcrops of the 

 Lower Siluric in Canada. Spencer [1884] described a number of graptolites 

 from the Upper Siluric of Canada and the West. A systematic exploitation 

 of the graptolites of North America was conmienced by Gurley [1896], but 

 unfortunately the work has not been continued. Ruedemann has published 

 observations on graptolites of the Utica shale [1895] and in later years 

 undertaken the investigation of the "Hudson river shales" of New York, 

 demonstrating their composition of a series of graptolite zones, ranging from 

 the Upper Cambric to the Upper Champlainic [1901, 1902, 1903]. 



The elucidation of the morphology of the graptolites, of their internal 

 characters, of the structure of the proximal portions and of the mode of 

 development has met an almost prohibitive obstacle in the flattened condition 

 of the shale material ; and only the untiring patience of some observers and a 

 few fortunate discoveries of superior material have from time to time brought 

 forth essential facts. 



As, in the discussion of the morphologic characters of the graptolites, we 

 shall have occasion to recur in greater detail to the views of preceding 

 observers, it suffices here to mention only the most important advances made 

 in this branch of graptolitology. 



The first resolutely to attack the problem of the internal structure of the 

 graptolites was Barrande. He first asserted the invariable presence of a 

 solid axis or '^ virgula " in graptolites, introduced the term " common canal " 

 for the tube connecting the cells and claimed that forms with a double row 

 of cells have also a double common canal. Barrande also held that the 



