212 PALAEONTOLOGY OF ILLINOIS. 



Amphoracrinus subturbinatus, M. and W. 



PI. 15, Fig. 4 a, 4 6. 



Actinocrinua (Amphoracrinus) subturbinatus, Meek and Worthen, Sept., 18G0. Pro- 

 ceed. Acad. Nat. Sci., Philad., p. 388. 



Body rather under medium size, turbinate or obconical below 

 the arms, and depressed convex above; expanding regularly 

 with straight sides from the column to the summit of the third 

 radials, thence more abruptly to the arms; composed of flat, 

 smooth or merely granulose plates, which are connected by 

 close-fitting sutures. Interradial and anal spaces rather dis- 

 tinctly sinuous between the groups of arms. Base compara- 

 tively small, subpentagonal, about one-third as wide as high, 

 and not provided with a projecting rim; columnar facet small, 

 concave, less than half as broad as the base. First radial 

 plates generally a little wider than long, widening from the 

 base to the lateral angles, two of them heptagonai and three 

 hexagonal. Second radials small, about twice as wide as long, 

 quadrangular, or rarely with one of the upper angles slightly 

 truncated, so as to produce a fifth angle. Third radial pieces 

 a little larger than the second, about twice as wide as high, 

 hexagonal and heptagonai, and supporting on each superior 

 sloping side, in the anterior and posterior rays, one small sec- 

 ondary radial piece, each of which gives rise to two first bra- 

 chial pieces, while in each of the two antero-lateral rays, the 

 two small secondary pieces are truncated above, and each sur- 

 mounted by a single brachial piece; making two arms to each of 

 these rays, and four to each of the others, or sixteen to the 

 entire series. 



The first interradial plates are about two-thirds as large as 

 the first radials, nearly or quite as long as wide, and six to 

 eight sided. On the superior sloping sides of these, rest two 

 smaller pieces, which partly support the secondary radials, and 

 are surmounted by two or three irregular pieces, which extend 



