MELOCRINID 2. 311 
of the interradial plates is invariably the same at all sides, but at the anal 
side the ventral disk has a few additional pieces, and the plates pierced by 
the slits are shorter. The disk contains large orals, pushed anteriorly by 
the stout, almost central anal tube, and it has well defined radial dome 
plates of a first and second order. Ambulacra subtegminal. Column large, 
round; the sides covered in some of the species by large angular processes 
or ribs; axial canal very large and pentalobate. 
Distribution. — Restricted to the Upper Helderberg and Hamilton groups 
of America. 
Type of the genus. — Dolatocrinus lacus Lyon. 
Ltemarks.—The complete anchylosis of the basals, the large size of the 
first interbrachial and its being followed by a single plate, the large anal 
tube, and the slit-like openings at the sides of the arms, together with the 
perfect symmetry of the dorsal cup, form excellent characters of this genus. 
Lyon described the base as composed of five pieces, while Hall mentions 
three basals, but the fact is that the sutures are not visible externally in the 
specimens. Mr. Victor Lyon, however, sent us a specimen in which the 
presence of three plates is indicated at the inner floor, while no suture 
lines appear exteriorly. 
The slit-like openings have not been noticed before. We regard them as 
analogous to the respiratory pores of Batocrinus, from which, however, they 
differ in number, form and arrangement. 
Hall, in 1862, described several species of the type of Dolatocrinus under 
Cacabocrinus, a catalogue name of Troost, and among them Cacabocrinus 
Troosti and C. lamellosus, of which we have been unable to get authentic 
specimens. The descriptions are too general for specific identification. 
Dolatocrinus lacus Lyon. 
Plate XXVI. Figs. Ga-c. 
1857. Lyon; Geol. Rep. Kentucky, Vol. III., p. 482, Plate 4, Figs. 2, 2a-c. 
1881. W. and Sp.; Revision Paleocr., Part IT., p. 126. 
Calyx depressed hemispheric, flattened below, somewhat tumid around 
the summit. Dorsal cup more than once and a half as wide as high; the 
basals and the lower half of the radials deeply incurved, and formed into an 
inverted funnel-shaped concavity, which is wider than the column, the latter 
touching only the bottom part. The upper half of the radials, and nearly 
