370 



Review of the New York Geological Reports. 



D 



If 



fossils are to be received as evidence, these, says Dr. E., go far to 

 confirm this view. 



Now on comparing this list with the fossils of the Trenton 



limestone given in the New York Reports, we find only two 



common to the rocks in question, viz. Leptcena sericea and Bel- 

 Icrophon bilobatus, and closer observation might perhaps even 

 prove these to be distinct from the English fossils of this name. 

 Moreover these very fossils are not peculiar to the Bala limestone, 

 but are also Caradoc and Llandeilo species. Indeed the very list 

 referred to is given by Murchison to show that the Bala limestone 

 cannot be considered as belonging to a system distinct from the 

 Silurian, inasmuch as these species are common also to the lower 

 Silurian, viz. to the Caradoc sandstone and Llandeilo flags. How- 

 ever, Dr. E. founds his principal proof of the geological position 

 of the Trenton limestone on other grounds ; inasmuch as it lies 

 beneath rocks equivalent to the Llandeilo flags, viz. the Utica 

 slate. But when we investigate the evidence of this equivalency, 

 we find it rests solely on lithologicai character.* The truth is, 

 there is not yet a sufficient number of facts before us to enable 

 eologists to decide upon their minuter points of identification. 

 Here terminate the important limestone deposits of the Cham- 

 plain division ; above are chiefly shales and sandstone. 



Utica Slate, (No. 3 of Pennsylvania and Virginia Reports.) Li- 

 thologically this deposit is not distinguishable from the black 

 slate intercalated with the Trenton limestone ; in fact, the geolo- 

 gists look upon it as a continuation of the same sedimentary ac- 

 tion, but distinguish it as a separate formation in consequence of 

 its embracing a few peculiar fossils. 



Plate 8, p. 57, Vanuxem's Report. 



1. Triarthus Beckii. 2. Graptolites dentatus 



* Mr. Hall says he has detected a small Linirula in the Utica slate, very simi ar 

 to one found in the Llandeilo fla^s. 





