4 
On the Silurian System. 87 
characteristic fossil, the scales of a fish termed Holoptychus no- 
bilissimus, figured in Murchison’s work on the Silurian system. 
This rock not only holds precisely the same place between the 
coal and the Silurian rocks, and contains the same characteristic 
fossil, but is the same in color and. mineral character, as the old. 
ted sandstone of England. — It occurs on the rail-road near Bloss- 
burg, Tioga county, sak tere whence I received.a fine speci- 
~-men last spring. The carboniferous system is also well devel- 
— F - oped i In this country, but the mountain limestone is rare and in’ 
thin depositions generally. 'The fossils, however, are othe Pee 
and well characterized in the shales and ironstone nodul e 
Next succeeding formation or system, the new red sandstone, 
is very limited, cage above it we find no trace of that interesting 
Series of rock, the oolites, lias, wealden, &c., but the cretaceous 
rocks are widely distributed. Finally, the tertiary formations, 
Corresponding to the eocene, and older and newer pliocene, stretch 
along nearly the w eae the seaboard. I have lately ascertained 
that the eocene or wer tertiary occurs in the bluff at Natchez, 
Mississippi. 
= top of the eries, have k found to: correspond with those 
‘ , ar ble m: ‘emains now to determine 
“hed ; far the ‘subdivisions of the Eng- 
e lish and “Amérienty "Sian roe can 65 detimnined. As I have 
| lately examined the splendid. work of Murchison with this view, 
is may be interesting to geologists to learn the result, although it 
is necessarily: as yet but an imperfect view of this important sub- 
ject. Beginning, therefore, with the Llandeilo flags, I will ob- 
serve that this formation in the New York geological reports was 
compared to the Trenton limestone, but since the examination of 
‘8 
Murchison’s work I find that the Llandeilo rocks are charaoteri-_ 
zed by two species of trilobites which are extremely rare in this 
country, and although they occur in the Trenton limestone, I 
cannot but consider them as evidence that the Llandeilo roc 
have been thinly deposited and subsequently swept away. 
Caradoc Sandstone. 
appears to correspond with the celebrated limestone of 
hte Falls, known by the name of Trenton limestone, which 
occurs in many places in the northeastern portion of New York 
and in Canada, and passing under the upper Silurian rocks, reap- 
* * 
