220 Cincinnati Society of Natural History. 
GLYPTOCRINUS DECADACTYLUS (Hall. ) 
(Plate XI., fig. 1. Vault of G. decadactylus, magnified three diameters. The arms have 
been broken downward and outward, so as to show the vault in its extension over the am- 
bulacral furrows. and the first joint of the pinnules on each side of the furrows. The open- 
ing on the vault is within the wrinkle, and can not be seen on this specimen. Fig. la, frag- 
ment of the lower part of an arm, showing the integument covering the ambulacral furrow, 
and the first joint of the pinnules on each side, magnified six diameters. Fig. 16, Trans- 
verse section of an arm magnified six diameters. It was not made from a prepared micro- 
scopic section, and may not therefore be stiictly accurate. Fig. le, fragment of a vault 
showing the supposed excurrent opening, magnified six diameters _) 
Definition. —The column is round, composed of alternately thicker 
and thinner plates, the former projecting, and perforated with a pen- 
tagonal canal. Calyx obconoidal, interradial and intersecondary ra- 
dial areas flattened in the lower half and. more depressed above, with 
intertertiary areas deeply sunken, and strong radial ridges. ‘There are 
five thick, sculptured, pentagonal, basal plates, about as wide as high, 
and about one fourth as large as the first primary radials. The lower 
part of the plates have a flange, which united forms a ring a little 
larger than the top of the column. 
The primary radials are 3 by 5, the first heptagonal, second hexagonal, 
and third heptagonal. Thesecondary radials are 2 by 10. The tertiary 
radials are 5 to § by 20, above which the arms are free. The regular 
interradial areas have one plate resting upon the primary radials, 
two in the second range, three in the third, two or three in the fourth, 
and above these fifteen or twenty small plates in each depressed inter- 
tertiary area. Intersecondary radial areas have one rather large plate 
in each axil, and a dozen or more smaller ones filling the depression 
between the tertiaries. Intertertiary areas have in like manner one 
plate in each axil, and several smaller ones above. Azygous area 
has one plate resting upon the primary radials, three in the second 
range, three in the third, three or four in the fourth, four in the fifth, 
and above these thirty or forty small plates filling the depression be- 
tween the tertiaries. A very strong ridge arises at the center of the 
first azygous plate, and extends straight up the center of the azygous 
area to the fourth range of plates, and continuing, gradually diminish- 
ing in size, seems to disappear at about the eighth plate, or between 
the second or third tertiaries. Arms twenty, long, rounded on the 
outer side and furrowed on the inner, and composed of cuneiform 
plates, each of which supports at its larger end a pinnule composed of 
joints three or four times as long as wide. The pinnules begin on the 
fourth or fifth tertiary. so that three or four occur on each side below 
the top of the vault. They are directed upward on each side of the 
extension of the vault, over the ambulacral furrow. 
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