312 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
the whole of the first costals, spread out horizontally; while the second 
costals and distichals turn straight upward. The ornamentation of the dorsal 
cup consists of two or three rows of parallel ridges, which pass out from the 
middle of the plates — with or without interruption — to adjoining plates, 
so as to form numerous concentric triangles. A more conspicuous ridge 
passes up and down the rays. Another, equally prominent, connects the 
radials laterally, and forms a pentagon around the basal concavity. The 
radials, first costals and first interbrachials are each surmounted by a promi- 
nent node, while the plates of the tegmen are covered with small, granular 
prominences. 
Basals small, almost completely concealed by the column; forming a 
conspicuous cone at the inner floor of the calyx. Radials larger than first 
and second costals together, their greatest width equal to their length; 
their upper lateral faces shorter than the lower. First costals once and 
a half as wide as long, the upper and lower faces somewhat convex. Second 
costals a little longer and wider than the first. Distichals 2 X 10 in the 
calyx; the lower one almost as large as the preceding axillary; the others 
small, and supporting the arms of which there are two to the ray. Arm 
bases projecting ; the ambulacral openings large. First interbrachials as 
large as the radials and first costals together; they rise to the height of the 
first distichals, and are followed by a single much smaller plate in the second 
row, and three still smaller ones above, which support three or four plates 
in the disk. Orals and radial dome plates well defined, larger than the inter- 
ambulacrals. Anal tube almost central. Column round; the axial canal 
large and pentalobate. 
Horizon and Locality.— Hamilton group ; in the limestone bed above the 
Black Slate ; Louisville, Ky. 
Type in the Lyon collection at Jeffersonville, Ind. 
Dolatocrinus Marshi Lyon. 
Plate XX VI. Figs. 1a, b, c, d. 
1869. Lyon; Trans. Amer. Philos. Soc., Vol. XIIL., p. 461, Plate 27, Figs. 2, 21, » 2. 
1881. W. and Sp.; Revision Paleocr., Part II., p. 126. 
Calyx of medium size, wider than high. Dorsal cup basin-shaped, the 
bottom deeply excavated and truncated to near the top of the second 
costals; the sides gently curving upward to about a vertical position; the 
