CRINOIDEA OF THE WAVEELY GEOUP. 167 



Arms comparatively long and slender, composed of a double series of 

 plates, rising from the second radial in pairs ; again subdividing on the 

 second supraradial in one division, and in the other divisions, on the 

 third or fourth plate above, giving, as far as can be determined, four 

 arms from each ray. 



Surface of plates obscurely marked by radiating lines of nodes. 



Column composed of alternating thicker and thinner joints. 



This species differs from P. contritus in having longer and more slender 

 arms, and but four from each ray. The calyx also differs from that one 

 in being nodose, at least on the radial plates; also, the basal plates are 

 smaller, and destitute of the projecting rim at their lower margins. 



In the separated basal portions, and in the first radial plates, this spe- 

 cies bears some resemblance to P. ehoraceus, of the Hamilton group of 

 New York. 



Formation and locality: In shales of the Waverly sandstone group, at Eichfleld, 

 Summit county, Ohio. 



Platyceinus Richfieldensis (n. sp.). 



Plate 11, fig. 1. 



Body broadly rounded, cup-shaped, approaching to hemispherical; 

 very slightly truncate at the base for the reception of the column, and 

 marked by a faint ring around the very small cicatrix. Basal plates form- 

 ing about one-half the height of the calyx, and proportionally very large. 

 First radial plates apparently wider than long, the exact proportions not 

 fully determined, their upper margins slightly excavated for the support 

 of the second radials, the scar extending not more than half the width 

 of the plate and very shallow. Second radials small, obtusely wedge- 

 form above; the lateral margins very short, and, in some of the rays, 

 apparently forming an edge. Interradial plates not observed, but the 

 species would indicate them as being of moderate size. 



Arms long, very slender, rising in pairs from the second radial, and 

 bifurcating on the second supraradial, so far as determined ; above this 

 bifurcation they are simple throughout, and gradually decrease in size, 

 the extremities being only thread-like ; composed of a double series of 

 obtusely wedge-form plates in the lower part, the sharp or narrow edges 

 of which extend nearly across the arm ; in the upper part the arm plates 

 are proportionally longer, and extend entirely across, but separating 

 very slightly the two adjacent plates on the opposite side, making a 



