RHODOCRINID 2. 243 
well proportioned. The calycine appendages pendent, unusually stout and 
long, and composed of cylindrical joints whose apposed faces are striated. 
The joints grow longer as they decrease in width, and at the end of the 
tubes are twice as long as wide; they are thicker in the middle than at the 
ends, and the median part is marked by a transverse row of little nodes. 
The tubes of adjacent ambulacra are united to their sixth or seventh joints, 
and the plates meet alternately by a zigzag suture. Interbrachials: 3, 3, 3, 
3, 2 — exceptionally two in the first row— the upper row abutting against 
the appendages. The anal side has an additional plate in the second row. 
Interdistichals about six to each area. Ventral disk pentangular in outline, 
with five interradial depressions; the posterior one, which contains the anus, 
larger; the plates of nearly uniform size and all convex. Orals undetermin- 
able. Anus more excentric than in the preceding species. Column large 
and round; the nodal joints higher and wider, their edges, like those of 
the intervening joints, slightly rounded. Avxial canal sharply stellate. 
Horizon and Locality. — Upper Burlington limestone, and Burlington and 
Keokuk Transition bed; Burlington and Pleasant Grove, Iowa. 
Type in the Worthen collection. 
Remarks. — We regard Hall’s Trematocrinus papillatus as a mere varia- 
tion of this species ; the spines of the plates being shorter and the calyx more 
robust. In the Revision, Part IL, p. 219, we erroneously placed it as a 
synonym under Gilbertsocrinus tuberculosus. 
Gilbertsocrinus tuberculosus (Hatz). 
Plate XVII. Figs. 5a, b, ¢. 
1859. Trematocrinus tuberculosus— Hau; Suppl. Iowa Geol. Rep., Vol.. I., p. 75. 
1881. Ollacrinus tuberculosus W. and Sp.; Revision Paleoer., Part H., p. 219. 
1889. Goniasteroidocrinus tuberculosus —S. A. Mutter; North Amer. Paleont., 250. 
In the form of calyx and arrangement of plates, this species closely 
resembles the preceding one, but the arms are erect instead of pendent, the 
appendages much shorter, and they taper rapidly to a point. Plates strongly 
convex or slightly nodose, the surfaces smooth. 
Infrabasals placed at the bottom of a shallow concavity, which is formed 
by the lower half of the basals, the upper half curving upwards, and taking 
part in the lateral walls of the calyx. Basals and radials considerably larger 
than any of the succeeding plates. Costals fully one half smaller than the 
radials. Distichals 410; the two lower, which are placed in the calyx, as large 
