286 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
Specimens small. Calyx obconical to subg!obose ; generally with promi- 
nent ridges along the radial and anal plates; the surface densely covered 
with very fine striz or small granules. 
Basals three, large, unequal, formimg a more or less deep cup; two of 
the plates equal, the other one half smaller, Radials very large; their upper 
corners but slightly truncated by the interbrachials. Costals two, small; 
rarely more than one third the size of the radials, and in some species still 
smaller. Of the distichals generally only the first plate takes part in the 
calyx, but occasionally also the second. Arms ten, long, biserial, and simple 
throughout. Interbrachials few. Anal area much the widest and quite 
distinct. It has three plates in the first row, of which the middle one is 
placed against the sloping upper faces of the two posterior radials; while 
the two smaller ones at the sides, together with the first costal, occupy the 
upper face of the plate, in a similar manner as the corresponding plates of 
the Platycrinidx, except that those of Macrostylocrinus do not extend beyond 
the limits of the dorsal cup. The middle or anal plate is generally followed 
by one or two other anals, longitudinally arranged. Ventral disk low; com- 
posed, so far as observed, of small irregular pieces. Column round; axial 
canal small. 
Distribution. — Restricted to the Niagara group of America. 
Type of the genus: Muacrostylocrinus ornatus Hall. 
Remarks. — This genus differs from all other Melocrinites in the number 
of basals, and in having in the anal interradius three plates in the first row, 
while the others have but one. The anal side of Hall’s diagram on page 150 
of the 28th Rep. N. Y. State Museum is incorrectly given, and it appears 
from the description that Hall was not aware that in Macrostylocrinus the 
arrangement of plates in the anal interradius differs from that of the other 
sides. The basals in that diagram are represented as equal, while in fact 
they are unequal, two of them being larger than the third. 
Shumard regarded this genus as identical with Cfenocrinus Bronn, from 
which it differs in the construction of the anal interradius — the latter 
having but one plate in the first row —and also in the number of basals. 
Macrostylocrinus ornatus Hatz. 
Plate XXIII. Figs. Sa, b, c. 
1851. Macrostylocrinus ornatus — Wat; Paleont. N. Y., Vol. IT., p. 204, Plate 46, Figs. 4a-g. 
1866.  Ctenocrinus ornatus —Suvumarp; Trans. Acad. Sci. St. Louis, p. 361. 
1881. Macrostylocrinus ornatus — W. and Se.; Revision Paleoer., Part IL, p. 103. 
