358 



PALEONTOLOGY OF ILLINOIS. 



ELJEACRINUS OBOVATUS, Barris., Nov. Sp. 



Body obovate or elongate-baloon shaped, 

 more than once and a half as long as wide ; 

 upper half wider than the lower, semiovoid ; 

 greatest width at about two-thirds from the 

 base ; lower half gradually increasing in 

 width to the distal end of the ambulacra; 

 base truncate with a deep concavity which is 

 'filled by the column. Cross section pen- 

 tangular, with straight or very slightly con - 

 diamete?8 arris ' Enlarged tw vex sides, except along the basals, where 

 the sides are somewhat concave, and the section more stellate. 



Basals deeply imbedded within the columnar cavity, the outer 

 angles barely reaching the margin. Kadials comparatively small; 

 length twice their width at the basi-radial suture, gradually increas- 

 ing upward, so that the forks or limbs at their upper side are about 

 equal in width to the body of the plate at its lower side. The lat- 

 eral sides are somewhat thickened at the upper face of the edge, 

 more particularly toward the lower end of the plate, where they 

 produce indistinct ridges at the suture lines. The upper side of the 

 limbs is gracefully curved in an upward direction, with re-entering 

 angles toward the lateral sutures, and deeper ones toward the radial 

 sinuses. From the bottom of the plate there extends to the radial 

 sinus (which in this species is about half way to the top of the 

 limbs), a conspicuous rounded ridge, ending in a very prominent 

 lip, and it is this structure mainly which produces the truncation 

 toward the basal region, which otherwise would not be very percep- 

 tible. 



Oral or deltoid pieces lar'ge, measuring almost four-fifths the 

 length of the body; broad lanceolate. The four regular orals have 

 a length equal to twice their greatest width. The fifth, that of the 

 posterior side, which in this genus is divided throughout its full 

 length by a large anal plate, occupies, including the latter piece, no 

 greater width than the four regular orals, and the two halves are 

 narrower at any place than the interposed anal plate. The latter 

 is lanceolate, of nearly equal width throughout, slightly tapering at 

 the upper end. Its lower side rests on the same surface with the 

 other plate, but gradually rises above the general level and at the 



