Oct., 1907. New Crinoids — Slocom. 279 



into the basal cavity. The three plates at the angles are larger than 

 the other two. The basal triangle is followed by three large plates 

 which comprise the principal part of the calyx. These are the an- 

 terior and left posterior radials and an inferradial plate. The left 

 posterior radial rests upon two basals, the other two plates rest upon 

 three. The other three radials are small, angular below and are not 

 in contact with the basals; the left anterior radial rests upon the 

 sloping sides of the adjoining radials, and the right posterior and 

 right anterior radials each rest, one side upon the inferradial and one 

 side upon the adjoining radial. The distal edges of the radials are 

 provided with short processes at their juncture with the lateral edges 

 which form a wide, shallow, angular excavation for the attachment 

 of the arms. 



Arms not preserved. 



Owing to the thickness of the plates, the natural casts of this genus 

 bear little resemblance to the exterior of the calyces. The natural casts 

 of this species are in the form of a triangular pyramid , truncated by a 

 cylinder. The base of the pyramid is nearly flat and is formed by the 

 inner surfaces of the basal plates. One face of the pyramid is formed 

 by the inferradial plate and the other two by the lower part of the 

 large radials. The cylinder is formed by the three small radials together 

 with the upper part of the two larger ones. 



The distinguishing characteristics of the exterior of the calyx of 

 this species are its globular form, with its depressed base, gradually 

 curving into the facet for the attachment of the stem. The casts are 

 distinguished by the triangular pyramid at its base. 



Locality: This species is comparatively abundant in the clay 

 pockets in the limestone at Romeo, Illinois, where it occurs as silici- 

 fied specimens which appear to be identical with those of the type 

 locality. In the spoil heaps along the Chicago Drainage Canal near 

 Lemont, Illinois, it is one of the most abundant crinoids in the form of 

 natural molds and casts, and a single silicified specimen was found 

 there. 



Pisocrinus benedicti S. A. Miller, Plate LXXXIV, Figures 8-1 1. 



1892. P. benedicti S. A. M., 17th Rept. Geol. Surv. Ind., p. 639, 

 PI. VI, Figs. 3-16. 



Calyx deeply cup-shaped, moderately expanding to the upper 

 third, rounded at the base and slightly constricted at the top; plates 

 thick, surface smooth or finely granular. 



The plates of the calyx are the same in number and position as 

 in P. gemmijormis, but the basals are larger than in that species, so as 



