174 F. B. Meek and A. H. Worthen on the Age 
not insisting, however, upon the exact identity of these forms, 
for that is a question that can only be settled by direct compari- 
son with authentic specimens of the European species; yet that . 
they are at least strikingly analogous, must be evident to any 
one who will but glance at Prof. Hall's, and Prof. DeKoninck’s 
ures 
ew we compare the two species of Nautilus now known, from 
the Rockford beds, NV. digonus, and N. trisulcatus, Meek an nd Wor- 
then, we find them wholly unlike any forms known in the Mar- 
cellus shale, while the latter species is allied to the Carboniferous 
N. suleatus of Sower y. (see Koninck’s An. Foss., pl. xlvii, fig. 
10), and the former is aaletaleie to two or three of the species 
figured by DeKoninck from the Carboniferous rocks of Belgium. 
In fact both of these species belong to a peculiar subgenus of 
Nautili for which we =< proposed the name TJrematodiscus, & 
group embracing a number of discoid Carboniferous species, 
with a wide perforated umbilicus and narrow whorls, which are 
ornamented with longitudinal angular ridges, and sometimes 
with parallel stri#. So far as we know, the entire group 
canted to the Carboniferous system, unless those found in the 
Rockford Goniatite bed and its equivalent in Illinois, are exX- 
ceptions,* 
In order to show the close relations between the Chouteau 
limestone and the Burlington (acknowledged loners beds 
above, in Illinois, we might give many sections, with of 
fossils, but the following taken near Grafton in Jersey sone 
will be sufficient for illustration :— 
1.—BuvRr.LINGTON LIMESTON 
presenting its catal cuarhote and containing its usual 
fossils; showing at the immediate outcrop where the sec- 
tion was taken, a thickness of 8 to 10 feet, but increasing 
as the country rises back to a thickness of 150 or 200 feet. 
2. CHourEAU LIMESTON 
Upper part rate of ash-colored rales shelly 
limestone in thin lares, with greenish marly partings and 
ensis, Strophomena rhomboidatis, Orthis ’ Michilini, 0. 
Sere ah wip red setts ? aihory 5h equila- 
tera. 
i 40 feet. 
The forms included in this subgenus differ so widely from the recent —. 
P saagad es of Nautilus, that few co aholegite would place them in the same genus} 
y 
N. stygialis, N. Répardiien aber v. ‘Omalians ve Koninck, and N, sulcatus, and 
N. cariniferous of Baenby. ype acile of Hall, from the Rockford lime- 
stone probably also belongs to this gro 
