ACTINOCRINID 2. 639 
forming shallow grooves along the sutures, which are in many specimens 
indistinct or concealed from view by the large adherent upper stem joint. 
Radials and anal plate very large, generally longer than wide, their lateral 
faces much larger than the others. First costals of the same form as the 
* radials, but a third smaller; the second a little shorter than the first. Suc- 
ceeding brachials to the margin of the rim about as long as wide, gradually 
decreasing upward, each one supporting an arm from one side, and an axil- 
lary of higher rank from the other — except the upper one, which supports 
two arms — the lower arm plates and their pinnules taking part in the rim. 
The arms from the distichals are incorporated to the sixth plate, those from 
the palmars to the fifth, and so on to the last bifurcation; the arms of the 
former being given off toward the outer sides of the rays, those of the latter 
to the inner; the first pinnule of each arm proceeds from the proximal plate. 
There are fourteen bifurcations in each main division of the ray, with as many 
as fifteen arms, or thirty to the ray, and one hundred and fifty to the species. 
But from the eighth bifurcation upwards the arms are semi-free— only the 
proximal plate of each arm being attached — and thus are in a similar con- 
dition to the arms of Steganocrinus (Plate LXV, Fig. 16). The free arms are 
~short, simple, and biserial. Interbrachials: 1, 2, 2,2, 2, 1 at the four regular 
sides, and 2, 3, 3, 3, 2, 1 at the anal interradius; the two upper rows forming 
part of the rim, being arched by the plates of the fixed pinnules of adjoining 
rays. The interdistichals consist of only one plate, which is arched by 
pinnules. Ventral disk covered by many thousands of small irregular pieces, 
which decrease in size as they approach the arms; those occupying the 
middle portions almost flat, those near the outer margins slightly nodose. 
Anus subcentral, small, the opening directed anteriorly. Column large, 
round; the nodal joints but little wider than the intervening ones, their 
edges covered with a row of small nodes. 
Horizon and Locality. — Upper Burlington limestone; Burlington, Lowa, 
Quincy, Hls., Hannibal, Mo., e¢e. 
Type in the (Worthen) Illinois State collection, Springfield. 
Remarks. — We obtained at Burlington a very large specimen of this 
species, which with stem and portions of the root measures about two feet in 
length; the width of the stem near the calyx is 8 mm.; its greatest width, 
about five inches from the lower end, 12 mm.; the width of the branchlets, 
domm. From the first branchlet, which is followed in the specimen by nine 
or ten others of nearly the same width, it tapers gradually to 6 mm., from 
