LOWER SILURIC SHALES OF THE MOHAWK VALLEY 27 



The heavy drift to the south has buried the " Utica " beds as 

 far as the " Frankfort " beds at the base of the Helderberg escarp- 

 ment. 



If we combine the observations of Canajoharie and Ffat creeks, 

 we obtain the following groups of faunules, indicative of larger 

 zones : 



1 Zone of Diplograptus amplexicaulis, 

 Corynoides calicularis, ostracods, lamellibranchs 

 (notably Pterinea (Prolobella?) trentonensis and 

 i n s u e t a , etc.). 



2 Zone of Glossogr. quadrimucronatus cor- 

 nutus, Corynoides calicularis, the ostracods, Cyatho- 

 dictya, Triarthrus becki. 



3 Zone of Lasiogr. eucharis, Lingula curta, 

 Schizocrania filosa, Trocholites ammo- 

 nius, Triarthrus becki. 



4 Zone of Climacogr. spiniferus, Diplogr. 

 vespertinus, Lasiogr. eucharis, Triarthrus 

 becki 



The first two zones have never, in our earlier work, been 

 observed in the Dolgeville section, while the base of that latter sec- 

 tion has furnished us a faunule identical with that of number 3. 

 To be sure of the absence of the lower two zones in the Utica 

 region, we have carefully searched the basal sections of the Utica 

 at Dolgeville and Jacksonburgh, three miles west of Little Falls, 

 where Cushing's map shows an exposure of the contact of Dolge- 

 ville (transition) beds and Utica shale; along the Starch Factory 

 creek at Utica ; and the exposure between Holland Patent and South 

 Trenton, recorded by Miller. In none of these localities were any 

 traces of the first two zones of the Canajoharie section found. On 

 Nine Mile creek near South Trenton, where the contact of the 

 Trenton and true Utica is exposed, Climacograptus 

 t y p i c a 1 i s is the dominant and characteristic graptolite of the 

 basal Utica. This typical Utica graptolite occurs there in immense 

 multitudes. It is associated with: 



Mastigograptus simplex (Walcott) 



M. tenuiramosus (Walcott) 



Pleurograptus linearis (Carruthers) 



Leptograptus annectans (Walcott} 



Dicranograptus nicholsoni Hopkinson 



Glossograptus quadrimucronatus (Hall), short, long spined 



variety 

 Cyathophycus reticulatus Walcott 



