ACTINOCEINID^. 559 



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. Eadials generally a little longer 

 than wide. First costals half the size of the radials, a little wider than lono-- 

 the second one half smaller than the first, and twice as wide as lono-. Dis- 

 tichals oue, quite small, giving off from the outer side an arm, from the inner 

 two palinars. 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 Avails are rarely intact. Arms forty, 

 moderately heavy, simple throughout, and biserial from the second or third 

 plate. Regular interbi'achials : 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 b}^ small almost flat ones. 



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

 and Monmouth and Quincy, Ills. 



Actinocrinus SCituluS Meek and WoETHEN. 

 Plate L V. Figs. 5, 6a, h. 



I860. M. and W. ; Proceed. Acad. Nat. Sei. Pliila., p. 3S6. 



1866. M. aiid W. ; Geol. Eep. Illinois, Vol. II., p. 202, Plate 15, Figs, la, b. 



lS8i: W. and Sp. ; Eevision Palteocr., Part II., p. 145. 



Syn. Actinocrinus msiines Hall; 1861, Descr. New Spec, of Crin., p. 2. 



Sjn. Adinocrinns Sillimani M. and W. ; 186], Proceed. Acad. Nat. Sci. Pliila., p. 134. 



Syn. Actinocrinns Wachsmuthi "W-bit-e; 1862 (not 1879), Proceed. Bost. Acad. Nat. Sci., A'"oI. 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 



