GRAPTOLITES OF NEW YORK, PxS.KT 1 589 



lets (" pinnules " Hall) ^^'llicll give to the colony a plumose appearance. 

 Stem round, smooth, slightly contracted between the bases of the pinnules ; 

 .3 mm wide; total length unknown ; ^^'ithout traces of thecal apertures in the 

 compressed state. Branchlets slender, filiform (width about .18 mm), ilexuous, 

 closely arranged, the branchlets of one side being only .6 mm apart, forming 

 an angle of 40*^ ^^-ith the stem, about 3 . 5 mm long ; showing, in the 

 specimen here described, no thecae, but often grooves in the middle as if com- 

 posed of slender tubes. 



Position and localities. In graptolite bed 7 of the Deep kill section, which 

 is a bed of soft shale at the dam, belonging to the zone with Diplo- 

 g r a p t u s d e n t a t u s . It is also frequent in beds containing a similar 

 congeries of fossils at Mt Moreno, near Hudson N. Y. Hall reports that 

 the two species of Ptilograptus, Avhich he described, were obtained in soft 

 shale associated Avith L o g a n o g r a p t u s 1 o g a n i , T e t r a g r a p t u s 

 quadribrachiatus, T. arcuatus, T. bigsbyi and others in 

 the Quebec group of Point Levis. This association would indicate the zone 

 with Tetragraptus, in which in the Deep kill section no specimens of this 

 species have been obtained. Grurley also reports the form as only occurring 

 in the Main Point Levis zone, and Ami observed it in material from Orleans 

 island, with L o g a n o g r a p t u s 1 o g a n i and Clonograptus 

 r i g i d u s . As it is very rare in the Deep kill bed, but more common 

 in the shale of Mt Moreno, -which contains a fauna transitional from a lower 

 zone to that with Dip log rapt us den tat us, and in Canada is reported 

 only from this lower zone, it ^vould seem to have its principal development 

 below the zone with Diplograptus den tat us. Billings found it 

 among the graptolites from Division P at the Cowhead, Newfoundland. 



Hemarhs. Hall supposed the fine transversal markings which also 

 appear on parts of the specimen figured here, to be thecal apertures 

 and concluded that the latter were arranged on one face of the 

 branchlets. 



