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788 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
gate convex and bordered by a groove; it has three rather large plates in the 
first row, and three in the second, followed by a moderate number of smaller 
pieces; the opening is directed obliquely upward. Posterior oral twice the 
size of the other four and spinous, while the latter are slightly convex. 
Radial dome plates large and tuberculous. The arrangement of the other 
disk plates is similar to that of the preceding species. 
Horizon and Locality. — (?) Kaskaskia group; Monroe Co., Ills. 
The type and only known specimen is in the Illinois State collection. 
Remarks. — Professor Worthen gives the horizon of this species as 
“Chester limestone,” which probably should be changed into upper part of 
St. Louis group. We infer this from the preservation of the specimen, and 
the fact that all the other species come from that horizon. 
Talarocrinus decornis W. and Sp. (nov. spec.). 
Plate LX XVIII. Figs. 3a, b, ¢. 
(?) Syn. Dichocrinus constrictus M. and W; 1869, Geol. Rep. Ills., p. 263, Vol. IL, Plate 19, Figs. 2a, 4, c. 
Smaller than any of the preceding species. Calyx once and a half as 
wide as high, elliptical in outline, the arm bases projecting, the interradial 
spaces depressed. Dorsal cup higher than the ventral disk; the plates con- 
vex and without ornamentation ; suture lines slightly grooved. 
Basals large, forming a rounded cup, which, viewed in profile, has about 
half the height of the radials; lower face of the cup a little concave. Radials 
erect, a shade wider at the top than at the bottom, about as wide as long ; 
their lower faces nearly straight, the upper excavated to one half their 
width at the middle, and the outer ends distinctly truncated for the reception 
of a small interbrachial. Anal plate a little longer than the anterior radial, 
the upper end somewhat inflected so as to form a well defined depression at 
the upper end. Distichals two; the lower one quite short, resting completely 
within the radial facets, and not coming in contact with the interbrachial 
: plate. Second distichals much larger, sharply angular above, and directed 
slightly outward. The first palmars take part in the calyx; the others are 
free. Arms four to the ray, biserial above the third or fourth plate; they 
are rather stout, rounded on the back, and composed of moderately long, 
slightly convex pieces, which interlock by a zigzag suture line. Ventral disk 
highly convex; the summit surmounted by an immense nodose plate. Inter- 
ambulacral spaces narrow, deeply depressed, having a single elongate plate 
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