GRAPTOLITES OF NEW YORK, PART 2 34 r 



worth in his manuscript report to Dr Gurley and the two most important 

 American varieties of the species have been elaborately described. Both 

 oi these valuable contributions to our knowledge of this species have been 

 incorporated in this paper [ p. 344H [.' 



Lapworth lias successively distinguished four subgenera of Diplo- 

 graptus, viz, Orthograptus and Glyptograptus [1874 | and Idiograptus and 

 Gymnograptus | 1880]. Two of these have strongly spinose forms for 

 types (O rtho g r a p t u s q u a d r i m u cronatus and I d i g raptus 

 aculeatus) which are here placed under Glossograptus and should, in 

 the writer's opinion, be regarded as subdivisions of that genus. Gymno- 

 graptus is a nomen nudum | 1880, p. 22] and according to a ms note of Dr 

 Gurley, based upon information from Professor Lapworth, allied or identical 

 with Idiograptus. This would leave Glyptograptus alone available for a 

 subdivision of Diplograptus as here conceived. Awaiting a final and more 

 complete grouping of the species of Diplograptus under Lapworth's super- 

 vision in the Monograph, of British Graptoiitcs, we have here refrained 

 from referring our types to any of these subgenera. 



Diplograptus appears in the last of the Deepkill zones, obviously 

 attains its climacteric development — -evinced in variety of forms, size 

 and multitude of individuals — in the Trenton shales and rapidly disap- 

 pears on this continent towards the end of the Champlainic, after shrinking 

 in both variety of form and size. 



Diplograptus foliaceus (Murchison) 



Plate 24, figures 1-8 ; plate 25, figures 1, 2 



? Fucoides dentatus (Brongn.) Conrad. N. Y. State Sur. 2d An. Rep't. 1838. 



p.114 

 ? Fucoides dentatus Vanuxem. Ibid. p. 283 



Graptolithus foliaceus Murchison. Sil. Syst. 1839. p. 694; pi. 26, fig. 3 

 ? Graptolites dentatus Vanuxem. Geol. N. Y. 3d Dist. 1842. p. 5 6 with fig. 



'Professor Lapworth desired to revise his views on 1). foliaceus and its varie- 

 ties expressed in this manuscript report and bring them into accord with those of the 

 Monograph of British Graptoiitcs but was unfortunately prevented from doing so. 



