The Galena a/)d Maqiioketa Series. — Sardesou. 31 
11. DiPLOGRAPTUS BED. 
Between the Triplecia bed and the Diplograptus bed there is a well 
marked stratigraphic change and one find,s the irregular strata of the 
former contrasted by the uniform laminas of the latter, except where 
concretionary structure has disturbed it. The change is not always 
from more calcareous strata to less calcareous ones as at Graf, Iowa 
and vicinity, but farther north is nearly the reverse as at Granger, 
Minnesota, where the Diplograptus bed is a brown carbonaceous 
limestone underlain by shaley strata of the Triplecia bed. 
The fauna is meagre in both pha.^es of this bed and local in charac- 
ter. Three species of Aaaphus, BeUeropJion bilohahiH Sow., Cy oto- 
lites ornaius, Conularia, and Diplogva2)inH are found in the limestone, 
and in the clay shale farther south are the last named with species of 
Liiigiila. Not one species is peculiar to this bed. At Dubuque, Iowa, 
and at Scales Mound, Illinois, one finds thousands of small fossils in a 
fine calcareous gravel that forms two or more thin strata near the base 
of the shales. They are secondary fossils and do not belong to the 
fauna of this time, but are evidently from the next older beds, having 
been torn from their matrix and transported, as the rolled and worn 
condition of the shells and interior casts shows. There are lacking 
among them many species from the next older beds of the locality, 
which would have been as easily transported as they, and hence they 
must have come a long distance from where local conditions had pro- 
duced a difference in fauna. 
The limestone in northern Iowa is 20 feet thick, and the clay shale 
equivalent at Graf, Iowa, is about the same, the division line there be- 
ing referred to a position close below the calcareous layers in which 
the Orthficeras are found. 
12. Orthoceras bed. 
At the north boundary of Iowa, in Howard county, this bed is of lime- 
stone 25 or more feet thick, that contains numerous quartz concre- 
tions and silicitied fossils, and that breaks up in it^ natural exposures 
into small cubical blocks much more than into slabs. It thins out 
northward or at least it is traceable only a few miles, beyond which the 
next higher bed (13) rests directly upon the Triplecia bed (10). South- 
ward as at Elgin, Iowa, it is 45 feet thick and is more shaley. From 
thence, it has not been traced continuously to Graf , Iowa, but at that 
place an exposure, as well known, exists and in it 20 feet of this and 
part of the next lower bed are seen. At that place the limestone is re- 
duced to a few mainly very fossiliferous strata between which are car- 
bonaceous clay-shale deposits. At Scales Mound, Illinois, the shale is 
almost without limestone. 
The fauna is not more constant than the sedimentary characters. 
In the limestones there are Ortltis einaaerata H., Murchisonia. niilleri 
H., Ctcnodwita. calrini Ulr., (Jletdo}>li<>r<>nii sp., Orthoeeras, Cijrtoceras, 
and in the shales are linguk)id shells and Diplogvaptns mainly, besides 
8on)e small fossils that appear to be secondary. The fauna of this bed 
