~ A ‘. . = = = — rn Eee a 
a —— =a — mes _ ce 
ACTINOCRINID.. 583 
tric. The ambulacra roofed by two rows of large covering pieces, which are 
more regularly arranged in young specimens (Fig. 5d), 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 found in the upper part of the Upper Bur- 
ington limestone; Burlington and Pleasant Grove, Iowa, and Marion 
Co., Mo. 
Type in the (Worthen) Ilinois State collection at Springfield. 
ftemarks. — 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 (Hatz). 
Plate LXI, Figs. 1a to f. 
1858. Actinocrinus sculptus —Hau; Geol. Rep. Iowa, Vol. I., Part IT., p. 582, Plate 10, Figs. lla, b. 
1866. Steganocrinus sculptus —Muxnx and WortuEn; Geol. Rep. Ilinois, Vol. IL, 1s JUS, 
1881. Steganocrinus sculptus —W. and Sp.; Revision Paleocr., Part IL., Datliosles 
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 which 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 large, 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 irrecularly 
axillary ; one of their upper faces short and distinctly sloping, the other 
