26 U. P. James—New Species of Fossil. 
countered three separate seams of lignite in short distance under — 
each other, and separated by clay and shale. Hames assumes 
that they are fragments of the same bed having been brought 
into its present position by a great slide.* 
Whatever may be the position of the strata in this locality, 
there can be no doubt that the granitic ledges of the Laurentian 
belt crop out in the vicinity, and that they are covered oy 
heavy timber. At Sauk Center, a village situated on the Sa 
river, forty miles west of the Mississippi, I found granite and 
diabase in parallel ledges, cropping out on the prairie. This 
place is only a few miles north of a line drawn from Richmond 
to Glenwood. The present bed and valley of the Sauk river 
can therefore safely be taken as nearly defining the northern 
limits of the basin. 
Further researches, to define the eastern and northern bound- 
aries of the great Cretaceous sea bordering on the Rocky Moun- 
tains, will be of great interest for the geology of the interior of 
the American continent. The future will probably show that 
Cretaceous strata are spread over a great area in Minnesota, 
resting on Laurentian, Huronian and Silurian rocks, and cov- 
ered partly by Tertiary deposits. 
St. Paul, Minnesota, October, 1871. 
Art. IV.—On a New Species of Fossil from the Lower Silurian ; 
by U. P. Jamzs. 
CYRTOLITES cosTaTuS. Body of shell nearly cylindrical: 
volutions about three, barely contiguous, enlarging rapidly ; 
aperture nearly circular, slightly expanded; surface marked 
by strong longitudinal costz, smaller costes coming in at dif 
ferent stages of growth, so that as they approach the aper- 
ture every third one is stronger and more elevated than the two 
between; strong transverse ribs or lines of growth at irregular 
intervals, with fine strie between; umbilicus large and deep; 
diameter of disk eight lines, but in this respect individuals of 
different ages must vary, as well as in the number intermediate 
costee. 
This species may be readily determined by the strong longi- 
tudinal coste and deep aatbttiewk : 
‘tion and locality.—Lower Silurian, Warren county, Ohio, 
about the middle of the Cincinnati group. Found September, 
1871. My cabinet. : 
* H. Eames, Geological Reconnoissance of the Northern, Middle and other Coun- 
ties of Minnesota, in 1866, St. Paul, 1867. 
