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624 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
Cactocrinus Arnoldi W. and Sp. 
Plate LVIL. Figs. 4a, b. 
1887. Actinocrinus Arnoldi —W.and Sr.; Geol. Rep. of Illinois (1890), p. 168, Plate 17, Fig. 10, and 
1890. Te a Arnoldi —8. A. Minter; N. Amer. Geol. and Paleont., p. 217. 
Of medium size, with long, slender spreading arms, and fan-like fringes of 
pinnules. Form of calyx subovate, gibbous below, spreading at the arm 
bases. The surface of the plates indented with numerous shallow pits and 
short grooves, whose rims, which are somewhat rounded off, connect with 
each other from plate to plate, and on the same plate in intersecting wrin- 
kles, all of which produces on the surface a somewhat irregular, cancellate 
sculpturing. 
Basals short, without projecting rim; the suture lines not grooved. 
Radials large. First costals hexangular, half the size-of the radials; the 
second still smaller and heptangular. Distichals and palmars small. Number 
of arms variable, from four to six to the ray,—six being the exception; they 
are heavier than in the preceding species, less crowded, and composed of 
a double row of very short pieces, united longitudinally by waving sutures; 
they are ornamented on the back in the upper portions by two rows of 
small nodes, one to each plate, in the lower portions by a more prominent 
node on every sixth or seventh plate. Pinnules long and in close contact, 
the proximal eight or nine joints provided with conspicuous hooks, directed 
upward, and forming with corresponding hooks of adjoining pinnules regular 
rows, parallel to the arms. Regular interbrachials six or more; the first 
equal in size to the first costals, the two of the second range to the second 
costals, the upper ones considerably smaller. The anal side consists of about 
eleven plates, the two upper ones resting between the arm bases, and in con- 
tact with the ambulacrals. Ventral disk depressed hemispherical, occupying 
less than one third the height of the calyx. It is composed of numerous 
very small pieces, of irregular arrangement and nearly equal size, most of 
them flat, with a few convex pieces scattered among them. Anal tube 
small, slightly excentric, abruptly rising from the ventral disk. Column 
composed of short joints of nearly uniform width. | 
Horizon and Locality. — Same as last. 
* See correction under Cacfocrinus ornatissimus. 
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rn ne eg eo — 
