20 



oblique, round-oval, with a slight expansion at the angle on 

 the upper side of the volution. Surface marked by close, 

 fine, equal striee of growth. 



Diameter *30 to 1* inch ; height '23 to '45 of an inch. 



Locality. — Spergen Hill ; Bloomington, la. 



This shell resembles the E. Icevis of D'Archiac and DeVer- 

 neuil (Trans. Geol. Soc. Lond., vol. vi, 2d series, part 2, p. 

 363, plate 33, fig. 7). E. planoi'bis in part of De Koninck. 

 (Carb. Fossils of Belgium, page 434, plate 25, fig. 7). 



Our shell agrees with the description of MM. D'A* and De 

 V., with the exception of the form of the aperture. The 

 figures given by these authors show the greatest diameter 

 of the aperture to be transverse, while in the species here 

 described the longest diameter is obliquely outwards and 

 downwards from the axis of the shell. Our shells with five 

 turns of the spire are much smaller than E. Icevis of these 

 authors, and our larger specimens are precisely of the same 

 size as the four inner volutions of their figure. 



It is possible, however, that these deviations which ap- 

 pear constant in our specimens may prove to be only a va- 

 riety not of specific value. Our specimens of this species, 

 which are numerous, do not lead us to include the E. planor- 

 bis of D'A. and De Y. as a variety. 



Euomphalus Spergexexsis var. plaxorbiformis. — Shell 

 discoid ; spire flat or concave; volutions about four, round- 

 ed above and below ; aperture nearly circular ; umbilicus 

 broad, not deep. 



Locality. — Bloomington ; Spergen Hill. 



Euomphalus plaxispira. — Shell discoid ; spire flat or 

 scarcely concave ; volutions about five or six, slender, very 

 gradually increasing in size, rounded above and below ; su- 

 ture well defined ; aperture circular ; umbilicus broad and 

 shallow. Surface marked by fine, closely arranged and 

 slightly undulating striae. 



Diameter '36 ; height '12 of an inch. 



Locality. — Spergen Hill ; Bloomington, la. 



