t 
On the Silurian System. os 89 
distinguished by different groups of organic remains. _ They pro- 
bably occupy more surface throughout the Union fis ay sa 
epee rocks. ’ ei 
Ludlow Rocks. 
These have not yet been subdivided; and they can only in a 
_ general way be compared with Murchison’s group. The organic 
‘Temains are in great numbers and variety, and are very unlike _ 
those of the lower Silurian rocks. 
The following table is given in order to correct some errors in 
- that published in the New York reports, and to show the relative 
ristic 
position of certain fossils which may be regarded as characte; 
Species. Though the table is necessarily incomplete, great care” 
has been taken to render i it correct as far as it goes, and I trust it 
will be found to convey.a novel view of the wonderful variety of 
Strata, each with its M see organic remains, which compose the 
Silurian syaieae 
ee - OLD RED SYSTEM. 
ae Characteristic Fossils. 
4 rod randstone, ptyehius noblisimus. 
a =e Pay 
SILURIAN SYSTEM. - 
Formations. . Characteristic Fossils. 
Dipleura Dekayi, Crypheus Greenii, Pterinea fas-) © 
22. Sandstoneand shales |} ciculata, Cyrtoceras maximum, C. gig ganteum, Or- S. 
of Cazenovia, &c. this orbieulatus, Orthoceras pyriforme, and man g 
aa unnamed bivalves. ; 
_ 21. Shales of Moscow ¢ Atrypa aspera, A. concentrica, Delthyris granulosa, | 2 
_ and Lake Erie, Crypheus calliteles. iy 
20, Onondagalimestone, § 7 ; Atrypa nasuta, I Delthyris, two species, (new,) Asaph- 
19. Oriskany sandstone, | a slongetty Delthyris arenosa; other large. bi- | 2 
18. Sandstone of Clarks- § A larg e © Orthoveras, Pterinea, (bilobite,) Calymene 
ville, Helderb “ 3 
ille, Helderberg, pla Ps 
17. Limestone of Clarks- S. mas tubifer. S 
16, Ristibons tag me per pe a 
15. Blue limestone, Delthyris, (ne = 
14, Shal li Trilobites, (wo new genera,) Delthyris macropleu- 3 
ata phat tae ra, Pileopsis? (yen ntricore ae (ip se (two spe- = 
reek, cies,) Sirophomtae costellat 2 
as 2 Fete lime- § Pentamerus (Atrypa) galeatus, Atrypa lacunosa. 
fap reneged ramos Delthris, (new,) Orthis, 
12. va limestone, (new,) Vv s univalves unnamed, Cytherina, a 
large soinieis 
Vol. xxxviuz, No. 1.—Oct—Dec. 1839. 12 
= 
a 
