A MONOGRAPH OP BRITISH GRAPTOLITES. 



INTEODUCTION. 



By the editor. 



A MoNOGEAPH upon the Britisli Grraptolites has long been a promised 

 pubhcation of the PalaeontogTaphical Society. It was originally undertaken by 

 the late Professor (Sir) Wyville Thomson about the year 1870. After his death 

 the late Professor H. Alleyne Nicholson and myself engaged to prepare a joint 

 Monograph, and for the last ten years or so I have been alone responsible. 



I have felt hitherto, however, that the time had not yet arrived for the 

 publication of such a Monograph. The wide interest in Graptolites aroused 

 in Britain and abroad within the last twenty years has been mainly due to the 

 demonstration of their extreme importance as " zoue fossils " in the stratigraphy 

 of the Lower Palfeozoic formations. The close attention thus called to these 

 fossils in the field, and their consequent collection in great abundance, has 

 had the effect of adding so largely to the number of new species and varieties, 

 and of so modifying our earlier views of the limits of the species previously 

 accepted, that the descriptive parts of a Monograph written during this interval 

 would have been practically obsolete before the work itself was completed. 



Again, notwithstanding the great amount of material collected and described, 

 oui- knowledge of the intimate structure of the Graptolites still remained far 

 behind our knowledge of the structure of other groups of fossils of like systematic 

 importance. Nor, until the recent results of the detailed methods of investigation 

 developed by Holm, Tornquist, Wiman, and others, began to be published, was 

 this department of the subject in a state sufficiently definite to admit of its being 

 treated in a manner worthy of a Monograph of the Palaeontographical Society. 



Further — and this was in reality the main drawback to the preparation of a 

 MonogTaph upon Graptolites having any pretension to accuracy and permanence, — 

 no method of illustration, except at great cost, had yet been arrived at by which 



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