168 PALEONTOLOGY OF ILLINOIS. 



cirrhi; there are no regular branches such as we find in most 

 of the Burlington species, and we doubt if this specimen, and 

 several others of other groups, occurring in the same locality, 

 were firmly attached when they died. 



Geological position, etc.: The same as that of the preceding- 

 species. 



Our own collection. 



ACTINOCKINUS ARNOLDI (nOV. sp.) W. fc Sp. 

 PL XVII. Fig. 10. A somewhat flattened specimen with arms and column. 



Of large size, with long, slender, spreading arms, and fan-like 

 fringes of pinnules. Form of calyx subovoid, gibbous below, 

 somewhat spreading at the arm bases. 



Basal disk low, discoid, convex toward the margins, with 

 slightly retreating angles to meet the radials; flattened for the 

 attachment of the column, but without projecting rim. 



First primary radials large, heptagonal; second hexagonal, 

 not more than one-half the size of the former; the third still 

 smaller. Secondary radials apparently small. 



Arms six to the ray on the anterior side; long, tapering 

 abruptly toward the top and growing very thin. They are 

 composed of a double series of very short interlocking pieces, 

 with waving suture lines. In the lower and middle portion of 

 the arms, every third to fifth arm piece bears on the back, 

 close to the longitudinal suture, a small, sharp, hook-like spine, 

 pointing upward. Toward the upper part, the arms have more 

 or less serrate edges, and the plates overlap each other, form- 

 ing at the back small, pointed hooks. 



Pinnules very numerous, long, slender, and in close contact as 

 if forming a reticulate fringe; each joint bearing a prominent 

 sharp hook, pointing at right angles to the pinnules. These 

 hooks, which run in 8 or 10 regular rows, parallel to the arms, 

 give to the mass of the pinnules, as they lie spread out, a 

 marked reticulate appearance. 



Interradials five or more, comparatively large. The first 

 equal in size to the second radials, the two in the second range 



