788 THE CEINOIDEA CAMEKATA 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, fohowed 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. 



Remarhs. — Professor Worthen gives the horizon of this species as 

 "Chester limestone," which probably should be changed into iq^jper part of 

 St. Louis group. "We infer this from the preservation of the specimen, and 

 tlie fact that all the other species come from that horizon. 



Talarocrinus decornis W. and Sp. (nov. spec). 

 Plate LXXVIII. Figs. 3a, b, c. 



(?) Syn. Bichocrinus constrMiis M. aud W; 1869, Geo!. Rep. Ills., p. 263, Vol II., Plate 19, Tigs. 2<r, b, 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. Eadials 

 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 iuterbracliial. Anal plate a little longer than the anterior radial, 

 the upper end somewhat inflected s6 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. Tnter- 

 ambulacral spaces narrow, deeply depressed, having a single elongate plate 



