ACTINOCRINID 2. osl 
Type in the (Worthen) Illinois State collection, Springfield. 
Remarks. — In the specimens from New Mexico, the entire surface of the 
calyx is covered with numerous irregular pustules, which are not represented 
in specimens from the eastern localities, 
Steganocrinus araneolus Merx and WortTHEN. 
Plate LXI. Figs. 2a, b. 
1860. Actinocrinus araneolus —M. and W.; Proceed. Acad. Nat. Sci. Phila., p. 387. 
1866. Steganocrinus araneolus— M. and W.; Geol. Rep. Illinois, Vol. II., p. 198, Plate 15, Figs. 1a, 0. 
1881. Steganocrinus araneolus — W. and Sv.; Revision Paleoer., Part IL., p. 151. 
This form in its general structure agrees so closely with the preceding 
one, that the question arises whether it is not a mere variety of that species, 
or perhaps its young stage. But the differences, such as they are, are so 
constant among a large number of specimens, that it has been deemed safer 
to treat it as a full species. It is not necessary, however, to give a repeti- 
tion of the general structure, but it will suffice to point out the special 
characters in which the two forms differ. 
Calyx from one half to one fourth the average size of S. pentagonus, and 
proportionally more depressed, its width to the top of the first costals equal 
to once and a half its height. The plates of the dorsal cup more tumid, and 
the ridges more prominent; those of the tesmen more evenly nodose. The 
basals are shorter, and almost invisible from a side view. It has but one row 
of distichals instead of two, and only the plate at one side of the ray is arm- 
hearing. There are, as in the other species, two brachial trunks from each 
ray, which stand out horizontally from the calyx, both arm-bearing, and each 
one giving off from twelve to fifteen armlets. The palmars of both ray 
divisions support an arm at the inner side of the ray, the post-palmars at the 
outer, and so on from alternate sides. As a rule, each successive order 
consists of a single plate, but there are occasionally syzygies, at which the 
arms are given off from the second plate, a fact which has never been 
observed in the other species. The arms are short, and their joints are not 
alternately spinous, but have serrated edges. In all other points this species 
agrees with the preceding. 
Horizon and Locality. — Same as last. 
Type in the (Worthen) Illinois State collection at Springfield. 
