GRAPTOLITES OF NEW YORK, PART 2 46 1 



sponding to late Niagaran), Bainbridge, Cape Girardeau co., Mo. Types 

 in U.lrich collection. 



Remarks. Since the Niagaran and its equivalents have as yet not fur- 

 nished an)' true graptolites and the two Clinton graptolites are the only 

 representatives in America of the rich European Monograptus fauna, the 

 finding of another Monograptid in the Siluric is of no little interest, and if 

 the form here described is indeed a Cyrtograptus, as we feel sure it is, its 

 importance is still enhanced as representing the occurrence in the North Ameri- 

 can continental sea of one of the most peculiar genera of the later Mono- 

 graptids, hitherto only known from the Atlantic, Bohemian and Baltic basins. 



In view of the fact that the species of Cyrtograptus furnish some of 

 the most important index fossils of the graptolite zones of the Siluric, it 

 • seemed further desirable to institute a closer comparison with the European 

 species and by a possible identification obtain a graptolitic datum plane for 

 our Siluric. While our form as judged from the secondary branches alone, 

 is specifically distinct from all of the European forms, it is obviously very 

 closely related to C . lundgreni Tullberg [1883, p. 39] from the Cyrto- 

 graptus shale of Scania and since that species is restricted to the zone with 

 C. carruthersi — the uppermost zone of the middle Siluric — both 

 occur in approximately equivalent beds and may be vicarious forms. 

 While the Scanian and Missourian species have the general form of the 

 branches and that of the thecae, especially also their lack of prominence 

 and their inclination in common, the branch of the American form is 

 notably narrower in its proximal portion and wider in the distal one and 

 also shorter. 



Since the thecae of Cyrtograptus are quite variable in form in different 

 portions of the rhabdosome, as Freeh has pointed out, a perfect identifica- 

 tion is impossible without a knowledge of the thecae of the main stem. 



The before mentioned lack of prominence of the thecae is a marked 

 feature of the branches ; in fact, the thecae, largely on account of their 

 small inclination and great overlap are so little projecting that of all the 

 many branches visible on the slab, only two or three were suitable for 



