FOSSILS OF THE CHESTER GEOUP. 557 



the column small, but distinct. Basal plates comparatively 

 large. pentagonal, their upper angles terminating at the 

 suture between the subradial plates. Subradials large, 

 nearly as wide as high, two heptagonal and three hexag- 

 onal, and all flat or slightly concave in the center, giving 

 a pentagonal form to the body. First radials pentagonal, 

 so far as can be seen in the specimen under examination, 

 wider than high, and contracted by curving inward at their 

 upper margins. Second radial or arm plate a little smaller 

 than the first radials, giving off a single arm from the right- 

 hand side, while on the left, there is a third radial or axil- 

 lary plate, giving origin to two arms on the single ray pre- 

 served. Arms, so far as can be seen, composed of rounded 

 plates, tolerably uniform in thickness, with well defined 

 sutures between them. 



This species may be readily distinguished from any one hitherto 

 known, by its concave sub-radial plates, and pentagonal outline. 



Position and locality Chester division of the Lower Carboniferous ; 

 < h ester, Illinois. 



AoAssizocKLtfus coxicus, O. and S. 



PI. 21, Fig. 8. 



Agasaizocrinvs 'conicus, OWEN and SHUMARD, 1851. Jour. Acad. Nat. Sci., Phila., n. s., VoL II, p. 93; 

 pi. 9, fig. 6. Also, Geol. Eep. Iowa, "Wis. and Minn., p. 597 ; pi 5, fig. 6. 



I'oxition and locality Chester division of the Lower Carboniferous ; 

 Chester, Illinois. 



PI. 21, Fig. 12. 



BASAL plates small, pentagonal ? slightly tumid, the up- 

 per angle projecting up between the subradials forming a 

 little star. Point of attachment for the column round 

 and very small. Subradial plates large, slightly gibbous, 

 three hexagonal and two heptagonal ; hight about one-half 

 greater than the breadth, gradually enlarging from the bot- 

 tom upwards, so that the greatest diameter is just below 

 the base of the first radials, from which point the body 



