58 NEW YORK STATE MUSEUM 



q 11 a d r i m u c r o n a t u s , all characteristic of the Utica shale of 

 the Mohawk valley. 



The aggregation shows the extension of the Utica shale fauna, 

 hitherto traced by its fossils only to the neighborhood of Albany, 

 into this southern belt of the formation and close to the boundary 

 of New Jersey, in which state the continuation of the same shale belt 

 has thus far furnished only the Normanskill (middle Trenton) 

 graptolite fauna. 



SPECIAL PROBLEMS 



Graptolites of New York. In 1905, part i of a monograph 

 of the graptolites of New York by Dr Ruedemann, Assistant 

 Paleontologist, was issued. This work embraced the species of the 

 earlier strata. The second part comprising species of the later 

 Lower Siluric, Upper Siluric and Devonic has been in preparation 

 for several years and is now completed. 



These faunas contain considerably more than 100 species, muta- 

 tions and varieties, all from the State of New York. The scope 

 of the work has, been extended as far as practicable to all the grap- 

 tolite shales of the United States, for while through Hall's pioneer 

 work in this field the graptolite shales of New York have furnished 

 the standard for all the graptolite beds of America, it is desirable 

 that the occasion of this revision of the New York faunas should be 

 used to compare these with those of the continent and to determine 

 as far as possible the paleogeographic distribution of the various 

 graptolite zones. One of the most interesting of these extralimital 

 faunas is the Normanskill (middle Trenton) fauna from Alabama. 

 This has been found directly between Trenton limestones, thereby 

 demonstrating the correctness of the conclusion arrived at before 

 by indirect evidence that the Normanskill graptolite shale is of 

 Trenton age. 



This second part contains an introduction ; chapters on the mor- 

 phology of spines ; on the disks in C 1 i m a c o g r a p t u s 

 b i c o r n i s ; on the vesicles upon the nemas in species of Diplo- 

 graptus and Climacograptus which are found to be inflations of 

 the outermost perisarcal layer, obviously serving to increase the 

 buoyancy of the rhabdosomes, and on the so called axis or virgula 

 of the Dicranograptidae which is found to be not homologous to 

 that of the other Axonophora, but of different secondary origin. 

 The composition of the successive faunal zones and their paleogeo- 

 graphic distribution are given, the careful comparison of the species 

 with those of other countries allowing more correct correlations 



