34 



ARTICULAT A. 

 SPIRORBIS, Lamarck. 



Spirorbis axnulatus. — Shell planorbicular, more or less 

 ascending, irregularly, spiral; spire composed of about three 

 turns, which are contiguous or more or less disconnected ; 

 umbilical side more or less deep and regular according to 

 the regularity of the spiral ; surface ornamented with strong 

 annulations, with finer striae between. 



Diameter from '062 to *25 of an inch. 



Locality. — Spergen Hill ; Bloomington, la. ; Alton, 111. 



//'Spirorbis annulatus, var. nodulosus. — 'Shell in form 

 like the preceding ; last volution strongly deflected ; volu- 

 tions sub-angular, marked by oblique striae or ridges which 

 become strongly nodolose on the umbilical side, and partic- 

 ularly towards the aperture. 

 Locality. — Spergen Hill, la. 



FORAMINIFERA. 



ROTALIA, Lamarck. 



//Rotalia Baileyi. — Shell depressed-orbicular, sub-equally 

 convex above and below, smooth ; margin rounded, indent- 

 ed by the septa ; spire depressed, involved ; last volution 

 slightly oblique, consisting of eight loculi ; aperture con- 

 tracted. 



The general form of this fossil is depressed-globular, with 

 the involutions deviating slightly from the same plane. Not 

 unfrequently, "however, the spire ascends in a greater or less 

 degree, and one or more loculi become visible beyond the 

 single volution. Sometimes seven loculi only are visible in 

 the volution. The surface is smooth under an ordinary 

 magnifier, and the outline is indented at the septa. 



This minute fossil is the first one of the Foraminifera 

 which has fallen under our observation in the carboniferous 



