728 THE CEINOIDEA CAMERATA OF NORTH AMERICA. 



Eucladocrinus tuberosus (Hall). 

 Plate LXXII. Figs. 3, 4 a, h, c. 



1838. Platt/crinm tuberosus — Hall; Geol. Hep. Iowa, Vol. I., Part H., p. 534, Plate 8, Figs. 7a, b. 

 1881. Pluti/crimis tuberosus — W. and Sp. ; Revision, Part II., p. 76 (Proc. Acad. Nat Sci. Phil., p. 250). 

 Syu. Plati/criiius occicleiUalis S. A. Millek, 1891 ; Geol. Surv. Missouri, Bull. 4, p. 10, Plate 1, 

 Figs. 5, 6. 



Calyx wider than high, liemisplieric to sub pyramidal, sliglitly pentangular 

 in outline. Dorsal cup di.scoid and very short, resting on the projecting 

 margins of the radial facets ; the lower edges of the facets directed slightly 

 downward, the limbs bending upward at a right angle. Ventral disk some- 

 what bulging at the posterior side, and portions of the interambulacral 

 plates visible from a dorsal aspect. Plates thin, without ornamentation, and 

 very little elevated ; the sutures slightly grooved. This species, in the form 

 of its brachial trunks, of which there is but one to the ray, and in the 

 arrangement of its arms, which are extremely short and given off in clusters 

 from the sides of the trunks, resembles certain .species of Oni/chocnnus. 



Basal disk proportionally small, with a small depression in the middle for 

 the proximal column joint. Interbasal sutures obsolete. Eadials subhex- 

 ao-onal, lying horizontally to near the facets, where they are twice as wide as 

 at the bottom. The facets occupy less than half tlie width of the plates ; 

 they are semi-elliptical, greatly projecting, directed more or less obliquely 

 downward; they are deeper excavated in the middle, and the margin is 

 obscurely striated. Calycine appendages heavy but short, their transverse 

 section oblong. They are directed obliquely downward to their full length, 

 and are composed of five successive orders of brachials, which give off arms 

 from the outer sides. The different orders, except the costals, consist of two 

 plates each, and are roofed by two series of rigid, very large covering pieces. 

 Costals extremely large, reaching a length of 6 to 7 mm. ; they are rounded 

 on the back, the sides abruptly curving inward, and the distal faces, although 

 axillary, almost straight. Distichals 2X2, a little wider than long and 

 quadrangular ; the second pentangular and irregularly axillary. The latter 

 plates give off 2 X 2 X 2 palmars, of which the outer ones support a cluster 

 of arms; while the inner ones take part in the calycine appendages. The 

 lower plates of the outer series are trigonal, and rest upon tlie sloping upper 

 faces of the distichals and against the sloping lower faces of the inner palmars 



