ACTINOCRINID^. 583 



trie. The ambulacra roofed by two rows of large covering pieces, which are 

 more regularly arranged in young specimens (Fig. 5b), in which the inter- 

 ambulacrals are less numerous. The same is the case with the orals, which 

 in the smaller specimens are in contact, but separated by perisomic plates 

 in larger ones. 



Horizon and Locality. — Only foimd in the upper part of the Upper Bur- 

 lington limestone ; Burlington and Pleasant Grove, Iowa, and Marion 

 Co., Mo. 



Tjfpe in the (Worthen) Illinois State collection at Springfield. 



Remarks. — Specimens of this and the two preceding species are most 

 commonly found with the axillary costals and all succeeding plates broken 

 off, which might give the impression, to a person judging by such a specimen 

 alone, that the calyx contained only one plate above the radials. 



Steganocrinus sculptus (Hall). 

 Plate LXI. Figs, la to f. 



185S. Actinocrhms sculptus — Hall; Geol. Rep. loTva, Vol. I., Part II., p. 582, Plate 10, Egs. 11a, b. 

 1866. Stegaiiocrims sculptus — Meek and Wokthen ; Geol. Rep. Illinois, Vol. 11., p. 197. 

 1881. Steganocrimis sculptus — W. and Sp. ; Revision Palteocr., Part II., p. IBl. 



Calyx rather large, biturbinate, somewhat higher than wide, the dorsal 

 cup but little higher than the ventral disk, its sides convex to the top of the 

 costals. The higher brachials bend obliquely outward, and their sides up- 

 ward, so as to form with the ambulacral plates above five long tubular 

 appendages, one to each ray, from whicli the arms are given off alternately 

 from every second plate at opposite sides. Plates thin, highly ornamented 

 with series of well defined angular ridges passing from plate to plate. From 

 the middle of the radials and anal plate, three to five of these ridges proceed 

 to the basals, three to the first costals, and 1, 2, or 3 to adjacent radials and 

 first interbrachials ; while there is generally but one ridge between the other 

 plates, of which that between the costals is decidedly the heavier and rounded 

 on the back. 



Basals moderately lai'ge, forming a spreading cup, with slightly angular 

 lower margin ; the interbasal sutures distinct but not grooved ; axial canal 

 large, and apparently circular. Radials about as wide as long. First costals 

 nearly one half smaller than the radiaLs, slightly wider than long, and hex- 

 angular. The second costals much smaller than the first, and irregularly 

 axillary ; one of their upper faces short and distinctly sloping, the other 



