612 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



Cactocrinus clarus Hall. 

 Plate LVII. Figs. 9 and 10, and Plate LVIII. Fig. 1. 



1861. Aetinocrims clans — Hall; Descr. New Spec. Grin. (Prelim, notice), p. 2; also Boston Joum. 

 Nat. Hist., Vol. VII., p. 277 ; N. Y. State Bull. Nat. Hist. (1872), Plate SA, Figs. 24 and 25. 

 1881. Ac.timcrinm clarus — W. and Sp. ; Revision Pateocr., Part II., p. 142. 

 1893. WniTriELD; Mem. Am. Mus. Nat. Hist. N. York, Vol. I., p. 8, Plate 1, ligs. 4 and 5. 



Larger than any of the preceding species. Calyx once and a half as 

 wide as high. Dorsal cup depressed subconical, broadly truncate at the base, 

 evenly spreading to the top of the costals, and more abruptly thence to the 

 arras. Ventral disk as high as the dorsal cup, somewhat expanded above 

 the arm bases, giving to the calyx a top-heavy appearance ; the anal tube 

 rising gradually from the summit. Plates of the dorsal cup heavy, and ele- 

 vated into strong angular nodes, which are either smooth or connected with 

 each other by short, indistinct ridges, except the palmars and post-palmars, 

 which are rounded off toward the sides, and separated laterally by deep 

 grooves. Suture lines distinctly grooved. 



Basals broad, rarely thickened at the lower margins, and projecting but 

 little beyond the column ; interbasal sutures well marked. Radials about 

 once and a half as large as the costals, as long as wide. First costals con- 

 siderably narrower; either quadrangular, pentangular or hexangular, the 

 second often larger than the first. Distichals as wide as the costals, but 

 shorter. Palmars a little narrower than the distichals, and twice as wide 

 as long, their outer plates supporting a single arm, the inner one two 

 with post-palmars, except in the two antero-lateral rays, in which only 

 one of the palmars is followed by higher brachials. Arm facets large, 

 equidistant, and directed horizontally. Arms twenty-eight, biserial from 

 their origin, heavy, long, and in close contact; they bend at first outward, 

 then gracefully upward, being rounded on the back, and showing no sign of 

 flattening or decrease in width to near the tips, where they rapidly taper to 

 a fine point. Arm joints arranged in parallel lines, quite short, and without 

 ornamentation. Pinnules long, fringe-like, composed of twelve to fourteen 

 joints, each one provided with a long, sharply pointed tooth-like projection, 

 directed obtusely upward and outward, which overlaps the corresponding 

 joint of the next pinnule above, their teeth forming raised lines parallel to 

 the sides of the arms. Regular interbrachials : 1, 2, 1 ; the three lower ones 



