RHODOCRINID^. 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 ^ve 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 wader, their edges, like those of 

 , the intervening joints, slightly rounded. Axial canal sharply stellate. 



Horizon and Locality. — Upper Burlington limestone, and Burlington and 

 Keokuk Transition bed ; Burlington and Pleasant Grove, Iowa. 



Tj/pe in the Worthen collection. 



Remarks. — We regard Hall's Trematocrinus papillatiis as a mere varia- 

 tion of this species ; the spines of the plates being shorter and the calyx more 

 robust. In the Revision, Part II., p. 219, we erroneously placed it as a 

 synonym under Gilhertsocrinus tuberciilosus. 



Gilbertsocrinus tuberculosus (Hall). 

 Plate XVII. Figs. 5a, h, c. 



1859. Trematocrinus tuberculosus — Hall; Suppl. Iowa Geol. Rep., Vol.. I., p. 75. 

 1881. Ollacrimis tuberculosus W. and Sp. ; Revision Palseocr., Part XL, p. 219. 

 1889. Goniasteroidocrinus tuberculosus — S. A. Miller; North Amer. Palseont., 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 4X10; the two lower, which are placed in the calyx, as large 



