328 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



Hadrocrinus discus Lyon. 

 Plate XXIV., Fig. 1, 



1869. Lyon ; Trans. Amer. Pliilos. Soc, Yol. XIH., p. 448, Plate 26, fig. a. 

 1881. W. and Sp. ; Revision Palseocr., Part IL, p. 222. 



A very large species. Dorsal cup flat-saiicer-shaped, the radials forming 

 a shallow concavity, of which the basals occupy the bottom, the radials the 

 sides. From the top of the radials to the second distichals the plates are 

 directed horizontally, and from there they proceed slightly upward to near 

 the arm bases, where they attain again a horizontal position. Plates moder- 

 ately heavy, apparently without ornamentation; shghtly concave, the median 

 space having a shallow circular pit, sometimes two being placed close to- 

 gether. Basals not visible in the specimens, and judging from the space 

 assigned to them, they were unusually small. Radials and costals small in 

 proportion; the former a little the larger, their lower faces one half the 

 width of the upper ; the upper sloping faces larger than the corresponding 

 lower ones. Second costals almost regularly pentagonal. Distichals 2 X 10, 

 larger than the radials, considerably longer than wide ; the first hexagonal, 

 the second pentagonal and axillary. Palmars 4 X 20 in the calyx, the two 

 lower ones as large as the distichals and of a similar form, the two upper 

 much shorter and slightly curved for the reception of the arms. Inter- 

 brachials nine or more, irregularly arranged, all nearly equal and as large as 

 the distichals. The anal interradius has three plates in the second row, which 

 are narrower than the two of the other sides. Interdistichals three, longi- 

 tudinally arranged, elongate, hexagonal, as large as adjoining brachials. 

 Structure of arms and ventral disk unknown. Columnar facet large, beauti- 

 full}^ striated. 



Horizorp and Locality. — Upper Helderberg group ; Falls of the Ohio, 

 near Louisville, Ky. 



Types in the Lyon collection. 



Hadrocrinus plenissimus Lyon. 

 FlaU XXIV., Figs, ^a, h. ' 



1869. Lyon ; Trans. Amer. Philos. Soc, Vol. XIIL, p. 445, Plate 26, Figs, d 1-3. 

 1881. W. and Sp. ; Revision Palseocr., Part II., p. 222. 



The specimens are fragmentary and crushed, so as to leave some doubt 

 as to the actual form and size of the calyx, except that it was depressed and 



