36 NEW YORK STATE MUSEUM 



At about the same level is the black shale at the base of the Ilion 

 section (230 feet below the Oneida conglomerate), which has 

 furnished: 



Climacograptus typicalis Hall 



Leptobolus insignis Hall 



Dalmanella testudinaria (Dalman) mut. (small) 



Dinorthis pectinella (Emmons) 



Rhynchotrema inaequivalve (Castelnau) 



Cf. Serpulites longissimus Murchison 



Triarthrus becki Green 



No fossils were observed until about 240 feet above the base, 

 where occur: 



3 Leptobolus insignis Hall 

 Orthoceras sp. 



The last fossiliferous shales were found directly below the top 

 (280-305 feet). They furnished: 



Climacograptus typicalis Hall (c) 



Orbiculoidea tenuistriata Ulrich (fide Ulrich) 

 Leptobolus insignis Hall 

 Orthoceras ( fragment ) 

 Triarthrus becki Green 



Of these fossils the Orbiculoidea tenuistriata 

 and the Triarthrus becki were found in the shale directly 

 below the Oneida conglomerate. 



It is obvious that these small faunules lack the essential elements 

 of the Lorraine fauna and do not appear to consist of more than 

 an impoverished Utica fauna. We see the strongest evidence of the 

 close faunistic relation between the Utica and Frankfort periods in 

 the uninterrupted persistence of Climacograptus typi- 

 calis through the whole of the Frankfort shales. 



As it will be shown in the next chapter that the beds in the lower 

 and probably middle Mohawk valley which have been hitherto re- 

 ferred to the Frankfort are of much older age, the Frankfort 

 formation disappearing eastward by overlap and the relations of 

 the typical Frankfort beds of the Frankfort section westward and 

 northward have not yet been studied in detail, it becomes necessary 

 to restrict for the present the term Frankfort shale to the formation 

 as exposed in the Utica region. The formation thus restricted has 

 its basal limit defined by the top of the true Utica, while the upper 

 boundary, which in the Utica region is formed by the Oneida con- 



