PALEONTOLOGY OF IOWA. 665 



SURFACE marked above by stride parallel to the lines of 

 growth, which, on the last volution, disappear in passing 

 over the angulate periphery : base of last volution marked 

 by strong revolving lines on the space between the outer 

 margin and the umbilical area. Base deeply excavated about 

 the umbilical region, but the umbilicus is unknown. Aperture 

 subquadrate ; upper edge of the outer lip projecting far over 

 the lower. 



Diameter -60, height *48 of an inch. 



Fig. 13 a. View of the summit, natural size. 



Fig. 13 b. Profile view, showing the elevation of the spire. 



Fig. 13 c. View of the base. 



Fig. 13 d. Enlargement of the striae and carinations which characterize the surface. 



Geological formation and localities. In limestone of the age of the War- 

 saw limestone : Spergen hill and Bloomington, Indiana. 



Capulus acutirostris. 



PLATE XXIII. FIG. 14 a, b. 



Capulus acutirostris : HALL, Transactions of the Albany Institute, Vol. iv, 1856. 



SHELL obliquely conical, more abruptly contracted above, 

 and continued in more slender proportions to the apex, which 

 is incurved, making about a single volution without contact 

 with the body of the shell : aperture subcircular ; margin 

 sinuate. 



SURFACE subplicate, with narrow subangular folds and 

 wider depressed spaces : lines of growth strong, abrupt upon 

 the angles, and arching forwards on the spaces between. 



This little shell is a very common and characteristic species of this rock ; and 

 though sometimes attaining a greater size than the figure, rarely varies from the 

 characters here assigned. 



Fig. 14 a, b. Views of the upper and lower sides of the shell. 



Geological position and localities. In the Warsaw limestone : Warsaw, 

 Illinois ; Spergen hill and Bloomington, Indiana., 



[ IOWA SURVEY.] 84 



