618 THE CEINOIDEA CAMEEATA OE NOKTH AMERICA. 



slightly projecting outward. Arm openings almost equidistant, the respira- 

 tory pores small. Arms eight to the ray, when normally developed, but 

 rays with seven or even six arms occur quite frequently ; they are somewhat 

 flattened, and composed of two series of transverse, rather short and appar- 

 ently smooth pieces. Eegular interbrachials : 1, 2, 2, 1 in mature speci- 

 mens; the first the same size as the first costals, the upper one very narrow, 

 and wedged in between the upper row of brachials. Anal plate followed by 

 2, 3, 2, and 1 plate. Ventral disk depressed conical, the plates near the 

 summit rather large and sharply nodose, those near the arm bases somewhat 

 smaller. Anal tube long, moderately thick, composed of short, transverse 

 pieces, with sharp, projecting edges. Column of medium size, the joints 

 rather short, the nodal ones distinctly angular and slightly projecting. 



Horizon and Locality. — Lower Burlington limestone ; Burlington, Iowa. 



Type in the (Worthen) Illinois State collection. 



Jiemarks. — Approaching C. coeMus in the form and ornamentation of 

 the dorsal cup, but the tegmen of that species is comparatively higher, 

 more conical, and the plates of the anal tube are larger and more nodose. 



Cactocrinus ccBlatus Hall. 

 Plate LIX. Figs. 8, 9. 



1858. Actiiwcriims ecelatus — Hall ; Geol. Rep. Iowa, Vol. I., Part II., p. 5S5, Plate 10, Pigs. \ia, i. 

 1881. Adbiocrinus ccelaUis — W. and Sp. ; Revision Pateocr., Part II., p. 143. 



Larger than the preceding species. Calyx short-subfusiform and highly 

 ornamented. Dorsal cup one fourth wider than high ; uniformly spreading 

 from the basals to the top of the arm-bearing brachials. Ventral disk sub- 

 conical, almost as high as the cup, the upper part drawn out, and passing 

 imperceptibly into the anal tube. The cup ornamented as in C. nmlti- 

 hrachiatus, except that the costals are connected among themselves and 

 with the radials by three parallel ridges, in place of one, as in that 

 species. 



Base short ; the sides neither spreading upward, nor projecting on the 

 lower margin; the lower surface sufficiently excavated to enclose the first 

 stem joint ; interbasal sutures distinctly grooved. Eadials a little wider than 

 long, and much larger than the costals. The higher brachials arranged 

 as in C. mulitbrachiatus. Arms eight to the ray, slender ; gently curving at 

 their bases outward and upward ; the tips, so far as observed, not incurving, 



