624 GEOLOGICAL SURVEY OF IOWA. 



A comparison of specimens with the authentic original of Prof. TROOST shows 

 no important differences of character. The specimen figured is vertically compressed, 

 and the figure of a better preserved specimen has been omitted by mistake. 



Fig. 8. View of the exterior of the base. 

 Fig. 3. Interior of the cup. 



Geological formation and locality. In the Keokuk limestone : Warsaw, 

 Illinois. 



Cyatliocriims bullaius ( n. s.) 



PLATE XVIII. FIG. 1 a. 



BODY somewhat irregularly hemispheric : base small, 

 pentagonal. Subradial plates very tumid, hemispherical, 

 extending much below the plane of the base in broad sub- 

 spheroidal prominences. First radial plates short : two of 

 them very tumid ; the others shorter, wider, and scarcely 

 tumid. Second and third radials very short and wide. Arms 

 dividing on the last radial : arm-plates almost entirely 

 circular, with a deep narrow groove on the inner side. Co- 

 lumn apparently subpentangular. Surface finely granulose, 

 with distinct prominent small granulae. 



Fig. 1 a. View of the base and a part of two arms. [ The subradial plates are not re- 

 presented as sufficiently prominent or globulose.] 



Geological position and locality. In the Keokuk limestone : Green coun- 

 ty, Illinois. 



Cyatliocriims tiuiiidus ( n. s.). 



PLATE XVIII. FIG. 1 b, c. 



CALYX basin-form, shallow, the plates thick and tumid. 

 Basal plates small ; their area nearly occupied by the co- 

 lumn, and presenting a small pentapetalous opening in the 

 centre. Subradial plates with the bases nearly straight, pen- 

 tagonal, except the one on the anal side which is hexagonal ; 

 each plate prominently convex or tumid. Radial plates some- 

 what unequal, very thick and broad, convex in the middle ; 

 articulating faces nearly in a plane with the axis. First anal 

 plate quadrangular, small. 



