3 GO NEW YORK STATE MUSEUM 



These differences are to some extent illustrated by the figures here 

 given, notably in the synrhabdosomes, though no attempt could be made to 

 bring out by special figures these more accidental features. Some discrep- 

 ancies in the descriptions which have been given of this species, are 

 undoubtedly due to these greatly differing aspects. Thus Hall describes 

 the thecae as consisting " of simple notches or transverse slits in the oppo- 

 site sides, which are slightly indented in the noncelluliferous face " and 

 though this is the most frequent aspect of the thecae, there are others from 

 Lake St John which distinctly show the projecting thecae. 



To this protean character of its aspects is also partly due the extended 

 failure to recognize this form which is the most common and evidently also 

 the most typical graptolite of the Utica shale in New York and Canada. 

 The story of this failure is revealed by the before-given synonymy. Hall 

 described the species in 1865 from the well-preserved material of Lake St 

 John in Canada and cited this locality alone as its place of fossil occurrence. 

 In 1847, in the first volume of the Palaeontology of New York, he had 

 described under one caption, both the common graptolite from the Xor- 

 manskill shale, D i p 1 o g r a p t u s foliaceus and G . q u a d r i m u c r o- 

 natus, referring both to Hisinger's species G rap toli thus prist is. 

 Most of his drawings of that species belong to G . q u ad r i m u c r o n a t u s. 

 The superior state of preservation of the rhabdosomes of the St John mate- 

 rial to that from the Utica shale of New York accounts easily for his failure 

 and that of all others, the present writer included, who have studied the 

 New York collections, to properly identify this common fossil. While the 

 occurrence of G. quadrimucronatus in the British beds had mean- 

 while been recognized by Nicholson and Lapworth and a Swedish horizon 

 had received its name from it by Tullberg, Gurley cited still in 1896 G. 

 (| u a d r i m u c r n a t u s from its Canadian locality only. When the pres- 

 ent writer discovered whole colonies (synrhabdosomes) near Dolgeville and 

 laid these before the venerable master of New York paleontology, they 

 were unhesitatingly referred to D i p 1 o g r. p r i s t i s and, since the Ameri- 

 can "prist is" had meanwhile been claimed to be identical with 1). foli- 



