LOWER SILURIC SHALES OF THE MOHAWK VALLEY 59 



known; and by the relations of the beds to the Canajoharie shale 

 and the new fossils discovered the inference of the Trenton age 

 of these shales has been much strengthened. 



While we have little doubt of the approximate equivalency of the 

 Magog shale with this shale of the Hudson valley, the fact that the 

 former contains only a graptoiite fauna, while the shale in the Hud- 

 son valley carries a mollusk fauna and that but few graptolites are 

 common to the shale in Quebec and that on the Hudson, suggests 

 that in the present state of our knowledge, at least, it is more appro- 

 priate to distinguish the two terranes by different names, especially 

 also since we do not know whether the two are continuous and 

 deposits of the same basin. Our reason for identifying the two 

 shales was the occurrence in both of certain graptolites, nota- 

 bly Climacograptus caudatus, C. scharen- 

 bergi, Cryptograptus tricornis and species of 

 Corynoides. All these are, however, European species which very 

 well might have entered the different channels in the Appalachian 

 system of troughs from the Atlantic basin to the east, as for instance 

 through the St Lawrence region and the New Jersey inlet. 



On account of the large faunas obtained on Snake hill on the 

 east shore of Saratoga lake we will designate these shales as Snake 

 Hill shales. Their lithologic character and their section on the east 

 shore of Saratoga lake will be fully described in the Schuylerville 

 quadrangle to be published together with the Saratoga quadrangle 

 by Professor H. P. Gushing and the writer. 



A large list of fossils Avere recorded from this formation in a 

 former publication (title 47), but this original list needs revision, 

 since a great many of the species had been only compared with 

 New York Lorraine forms under the assumption of the upper 

 Utica and Lorraine age of the beds. They have largely proven to 

 be earlier species, especially so among the lamellibranchs. Unfortu- 

 nately these earlier collections will not be accessible again for sev- 

 eral years to come. Nevertheless the list gives a fair idea of the 

 aspect and the size of the fauna of the Snake Hill beds. This large 

 fauna has been greatly augmented and partly corrected by the later 

 collections from Snake Hill itself, which are here listed as follows: 



Dicranograptus nicholsoni Hophinson (c) 



Diplograptus (Mesogr.) putilkis Hall (cc) 



Corynoides sp. (r) 



Glyptocrinus sp. (r) 



Heterocrinus ? gracilis Hall (c) 



Cremacrinus sp. (rr) 



