ACTINOCRINID 2. 509 
pass out to the basals, and single ones to the interbrachials and costals ; but 
these ridges, if present at all, are more or less obscure. 
Basals moderately large, forming a low cup, which is deeply notched at 
the sutures, and thickened at the lower margins so as to form a broad rim, 
which projects outwards and downwards. Radials generally a little longer 
than wide. First costals half the size of the radials, a little wider than long; 
the second one half smaller than the first, and twice as wide as long. Dis- 
tichals one, quite small, giving off from the outer side an arm, from the inner 
two palmars. The latter support an arm at the inner side, and two post- 
palmars with two arms at the outer, Arm facets with transverse, imperforate, 
articular ridge. The respiratory pores small, and placed so close to the am- 
bulacral openings that the intervening walls are rarely intact. Arms forty, 
moderately heavy, simple throughout, and biserial from the second or third 
plate. Regular interbrachials: 1, 2, 4, 5, followed by other plates in the 
tegmen ; those of the third and fourth row placed between the lobes, and in 
part interambulacral. _ Anal plate smaller than the radials; followed by 2, 3, 
4, or 6 plates, and by numerous smaller pieces in the tegmen. Plates of the 
tegmen sharply nodose and rather uniform in size, except the lower interam- 
bulacral pieces, which are somewhat smaller. Orals and radial dome plates 
indeterminable. Near the arm bases small covering pieces can be recog- 
nized. Anal tube almost central, large and heavy throughout; formed of 
rather large nodose plates, which are intermingled by small almost flat ones. 
Horizon and Locahty.— Upper Burlington limestone; Burlington, Iowa, 
and Monmouth and Quincy, Ills. | 
Actinocrinus scitulus Mezrx and WortTHEN. 
Plate LV. Figs. 5, 6a, 0. 
1860. M.and W.; Proceed. Acad. Nat. Sci. Phila., p. 386. 
1866. M. and W.; Geol. Rep. Illinois, Vol. IT., p. 202, Plate 15, Figs. 7a, 5b. 
1881. W.andSp.; Revision Paleocr., Part IT.,’p. 145. 
Syn. Actinocrinus rusticus Hati; 1861, Descr. New Spec. of Crin., p. 2. 
Syn. Actinocrinus Sillimani M. and W.; 1861, Proceed. Acad. Nat. Sci. Phila., p. 134. 
Syn. Actinocrinus Wachsmuthi Wuitn; 1862 (not 1879), Proceed. Bost. Acad. Nat. Sci., Vol. IX., 
p. 15. | 
Rather below medium size. In the form of the calyx approaching 
A. verrucosus, but the brachial extensions shorter, the interspaces nar- 
rower, and the interbrachials less numerous. Dorsal cup obconical, its 
4 
