REPORT OF THE STATE PALEONTOLOGIST 1901 551 



viz, the lowest, which then would appear to rest directly on 

 Oambric beds; or that they may, as suggested by the reported 

 identification of Dictyonema flabelliforme, belong 

 to an upper Cambric or transitional zone, and that the Cam- 

 bric may, therefore, be also represented in this slate belt by 

 graptolite shales. The fact that the middle and upper zones 

 found at the Deep kill seem to be absent in the outcrops re- 

 ferred to by Dale, may also account for the small thickness of 

 the terrane reported by that investigator, as compared with 

 that found at the Deep kill. 



A striking feature of the Deep kill section, and one worthy of 

 special notice, on account of the still contested nature of the 

 habitat of the graptolites, is the regular periodic succession of 

 the rocks associated with the black graptolite shales within 

 the two lower zones. To demonstrate these cycles of depo- 

 sition, the list of the beds is given in a more comprehensive 

 form. 



b limestones with shaly intercalations 



€ sandy shales and grits 



d greenish silicious shale and black graptolite shale 



e thin bedded shales, grits and limestone 



f greenish silicious shale and black graptolite shale 



g greenish silicious shale 



h limestone 



i greenish silicious beds and black graptolite shale 



j greenish silicious beds and sandy shales 



k limestone 



I greenish silicious beds and black graptolite shale 



m limestone 



n covered 



o greenish silicious beds and black graptolite shale 



It will be noticed that the deep black, soft graptolitiferous 

 mud shales are always inclosed in greenish gray, very hard, 

 thin bedded, more quartzose layers, and that between two 

 periods of deposition of these there is always intercalated one 

 of thin bedded, barren limestone. This alternation is pre- 

 sented five times in the section. 



