808 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
pieces of the anterior and posterior sides; by this arrangement the piece 
directed anteriorly is the only radial plate of this ring; five plates occupy 
the anal interradius, and the four other sides each have two. The fourth 
ring has sixteen plates; some hexangular, others pentangular, five of them 
radial, the others interradial; of the latter, five occupy the posterior side, 
one the postero-lateral sides, and two the antero-lateral ones. The fifth 
ring contains twelve plates, all of which are interradial and arranged in 
groups of 4, 2, 2,2, 2. At four sides, the two adjoining plates of different 
interradii meet radially by their lateral angles; but at the posterior side, 
which has four plates, the two middle ones are separated by plates from the 
fourth and sixth rings, which meet between them. Of the sixth ring, which 
is followed by the radials, five of the plates are radial, seven interradial ; 
three of the latter occupy the anal side, two the regular sides. There are in 
all seventy-eight accessory pieces, of which sixteen are radially disposed, the 
others interradially. The radial plates of the anterior side, and the plates of 
adjoining interradii together, are arranged exactly like the plates of the 
posterior side, there being in either case an uninterrupted series of four 
plates arranged longitudinally, and ten plates to each side; but, while the 
one row supports a radial, the other bears an anal plate. ‘The true radials of 
the species are larger than the plates which support them, wider than high, 
and hexangular; their truncated lower faces rest upon the radial plates of 
the preceding ring, the lower sloping faces upon the adjoining interradial 
pieces. The upper faces of the radials are excavated to three fourths their 
width into a rounded facet similar to that of Platycrinus. The anal plate 
is somewhat longer than the radials, but narrower. 
Horizon and Locality. — Coal Measures; Peoria Co., Ils. 
Type in the Illinois State collection at Springfield. 
Acrocrinus amphora W. and Sp. (nov. spec.). 
Plate LXXX. Figs. 4 to 9. 
Smaller than A. Schumardi. Calyx urn-shaped, more than twice as 
high as wide, gradually widening from the lower end to the middle, then 
contracting a little to the top of the radials. The plates thin, very slightly 
convex, and without ornamentation. 
Basals small for the genus, forming a rapidly spreading basin with a 
slight truncation at the lower end, corresponding to the width of the column. 
