HEX ACRINID.. Bou 
the summit somewhat flattened and covered by large orals, from which two 
rows of tuberculous covering pieces pass out to the arms. . Interradial spaces 
slightly depressed and paved by numerous rather large plates, all having 
a small tubercle in the centre; the anal interradius has five plates in the 
first row as against three at the other sides, and is very wide and bulging, 
the plates throughout being large, except those immediately surrounding the 
anus. The anal opening is placed near the summit in close proximity to the 
posterior oral. Column round, of moderate size, slightly tapering downward, 
the nodal joints but little wider than the internodals. 
Horizon and Locality. — Keokuk limestone; Crawfordsville, Ind. 
Types in the collection of the late Major Sidney 8. Lyon, Jefferson- 
ville, Ind. 
Remarks. — Dichocrinus expansus Meek and Worthen is undoubtedly iden- 
tical with this species, although the specimen figured has only six arms to 
the ray. Moreover, that name was pre-occupied by De Koninck and Le 
Hon in 1853. 
| Dichocrinus striatus O. and Suum. 
Plate LXXVILI. Figs. 11a, b. 
1852. Owen and Suumarp; U. S. Geol. Rep. Wisc., Iowa, and Minn., p. 590, Plate 54, Figs. 10a, d. 
1881. W. and Sp.; Revision Paleocr., Part If., p. 85. 
Calyx subglobose, widest at the basi-radial suture; composed of thin 
plates, which are thickly covered with conspicuous, abruptly elevated, longi- 
tudinal ridges. These ridges form around the calyx six well defined rhombs, 
which meet interradially at the basi-radial suture, the acute upper angles ot 
five of them reaching to the radial facets, that of the sixth to the upper part 
of the anal plate, and their lower angles to the lower ends of the basals. 
The rhombs are subdivided into two triangles by the basi-radial suture, and 
the included spaces are occupied by three or four vertical ridges, often with 
smaller ones between, which all cross the suture line unbroken. Other 
ridges, but less distinct and easily overlooked, fill the triangles formed 
between the upper sides of adjoining rhombs, and these as well as those 
within the rhombs, when examined under a lens, have an undulated outline. 
Basal cup hemispherical, slightly truncated at the lower end; column 
facet well defined and bordered by the lower ends of the ridges; height equal 
to that of the radials; superior margin distinctly hexangular. Radials quadri- 
lateral, narrower at the top than at the bottom; the width at the lower faces 
