. HEXACRINID^. 7S3 



Talarocrinus cornigerus (Shum.). 

 Plate LXXVIII. Figs. 6a, h, and 7a, h. 



1856. Diehocrhms eoniiffents — ^ms-n.kTi.11 ; Trans. St. Louis Acad. Sci., Vol. I., p. 73, Plate 1, Pigs. 



\a-d. 

 1865. Fterotocriims cornigerus— Shumakd; Catal. Palsoz. Poss. N. Araer., p. 393. 

 1877. Pterotocrimis cornii/erus—S. A. Miller; Catal. Amer. Pal-eoz. Foss. (1st Edit.), p. 89. 

 1881. Talarocrinus cornigerus — W. aud Sp. ; Revision PaIa?oer., Part II., p. 87. 

 1883. Talarocrinus cornigerus — S. A. Miller ; Catal. Amer. Palajoz. Foss. (2d Pdit.), p. 288. 



Calyx ovate, the base slightly truncated and excavated at the bottom. 

 Dorsal cup a little lower than the ventral disk, and somewhat shorter than 

 wide; the plate.s strong, moderately convex, but without other markings; 

 suture lines distinctly grooved. 



Basals forming a shallow cup, which is transversely elongated, and occu- 

 pies about one third the height of the dorsal cup ; it is concave at the lower 

 face, and the cavity is only partly filled by the column. Eadials sub- 

 quadrangular, slightly increasing in width upward, their length equal to the 

 greatest width ; the plates are a little tumid, the greatest convexity being at 

 two thirds their height, whence they slope considerably to the upper margin, 

 producing a moderate depression or constriction beneath the arm regions. 

 Anal plate considerably longer than the radials, its upper face on a level with 

 the top of the distichals, its lower face angular, the lateral faces parallel. 

 Costals and distichals very small, the former trigonal, often not visible 

 externally, and the distichals appear as if they rested upon the radials, as 

 described by Shumard ; they bend slightly outward, and are wider than 

 high, their upper faces concave, forming a sharp angle. First palmars 

 narrower and shorter than the distichals, rounded like arm plates ; the two 

 outer ones touching the radials. Arm openings four to the ray. The arms 

 are not preserved in any of the .specimens. Ventral disk highly elevated 

 and bulging ; the interambulacral spaces depressed, and the plates flat. 

 The radial dome plates strongly tuberculous, the other disk plates con- 

 vex. Posterior oral strictly central and of extreme size, forming a large 

 ovate tubercle, the shorter diameter facing the posterior and anterior 

 •sides. The other orals quite small and scarcely'- convex. Four of the 

 interambulacral spaces narrow, and the plates elongate; arranged 1, 2, 2, 

 with sometimes one or two small accessory pieces interposed between them. 

 The posterior interradius is wide, being composed above the anal plate 



