RHODOCRINID.. 239 
Gilbertsocrinus tuberosus (Lyon and Cass.). 
Plate XV. Figs. la, b ; Plate XVI. Figs 1 to6; Plate XVII. Fig. 6. 
1860. Goniasteroidocrinus (uberosus — Lyon and Cassepay; Amer. Journ. Sci., Vol. XXVIII. (Ser. 2), 
, 233. 
1866. Gilbertsocrinus (Goniasteroidocr.) tuberosus — Meek and WortuEN; Geol. Re. Illinois, Vol. IL, . 
220, with diagrams. 
1881. Ollacrinus tuberosus— W. and Sr.; Revision Paleoer., Pt. IL., . 219. 
1889. Goniasteroidocrinus tuberosus —S. A. Mitter; N. A. Geol. and Paleont., . 250; and 1891, Adv. 
Sheets 17th Re. Geol. Surv. Indiana, . 51, Plate 9, Fig. 11. 
Syn. Trematocrinus robustus Haut; 1860, Sul. Geol. Re. Iowa, . 77. 
Calyx large, a little higher than wide. Dorsal cup subeylindrical, 
slightly constricted at the arm regions, its base deeply excavated. Ventral 
disk flat, with deep interradial depressions; the appendages pendent, long, 
and frequently branching. Plates tumid, the radials drawn out into elon- 
gate nodes or obtuse spines, directed downward. 
Infrabasals small, almost completely covered by the column; forming 
the bottom part of the concavity, of which the basals constitute the sides, 
and the radials with large interradial plates between them form the rim 
of an inverted cone on which the remainder of the calyx rests. Radials 
longer than wide, considerably larger than the costals. The interradial 
plates large and covered with a sharp node. Costals hexagonal and hepta- 
gonal. Distichals two in the calyx, smaller than the costals, and about as 
wide as long. Arm openings of the same ray widely apart, separated by 
two or three interdistichals. Arms pendent, slender, branching, and with 
long pinnules; there being six ultimate arms to each arm opening. Caly- 
cine appendages in ten pairs, disposed interradially ; those of adjoining rays 
in sutural contact to about 12 mm. from the calyx, when the pairs separate, 
and the two tubes take a sharp outward turn, so that their tips meet with 
those of adjacent pairs. Each tube is composed of three rows of plates 
longitudinally arranged, two of them occupying the ventral, the third the 
dorsal side, so that there are six rows for the distance to which they are 
united. The tubes generally branch once or twice; they are long, and 
taper gradually to their tips. Interbrachials arranged longitudinally in 
three series of plates of nearly equal size; the anal side not distinct. Vent- 
ral disk low-hemispherical, almost flat, the plates highly convex, those form- 
ing the interradial depressions somewhat smaller, Orals a little larger than 
the other disk plates, and rather irregular in their arrangement. Anus 
