RHODOCRINID 2. 227 
strong, contiguous; composed of elongate joints. Interradial spaces arranged 
in four rows. The plates interposed between the radials smaller than these ; 
followed by two, rarely three, interbrachials, and these by two and three 
others in the two succeeding rows, which gradually decrease in size upwards. 
Anal side wider, with three plates in the second, and generally four in the 
third row. Interdistichals from two to three, very small. Disk slightly 
convex, the interradial spaces a little depressed ; constructed throughout 
of very small, irregularly arranged tumid plates. Anus almost central, at 
the end of a wart-like, somewhat conical protuberance, composed of very 
small pieces. Column round, from eight to ten inches long, nearly uniform 
for about two thirds its length, whence it gradually tapers to a fine point, 
with a few short cirri given off toward the end. The joints are rounded 
along their edges, and the nodal ones are a little the widest and longest. 
Horizon and Locality. — Kinderhook group, Le Grand, Marshall Co., 
Towa. 
Types in the collection of Wachsmuth and Springer. 
Remarks. — This species is one of the most abundant at the Le Grand 
locality, where many specimens have been obtained with crown and stem 
fully preserved. The specimens are invariably of a very dark color, though 
lying in contact with Platycrinus and other forms which are light colored, — 
sometimes almost as light as those from the Burlington rocks. This varia- 
tion in color of the fossils is one of the interesting facts of that locality. The 
Crinoids must have been deposited there in very quiet waters; they occur 
in a soft, light buff limestone, and in many cases are imbedded just as they 
died. They occur in nests or colonies, and the genera and species are indis- 
criminately commingled, there being of Crinoids and Blastoids upwards of 
twenty-four species. It is therefore a singular fact, that while the specimens 
of some species are of a pure calcareous composition, and of very light color, 
those of others, under precisely the same conditions of fossilization, lying 
side by side with them and often with stems and arms intertwined, are 
harder, and of a very dark, brownish or even purplish grey color. The 
contrast between some of them is very marked, and so nearly constant for 
the species as to be quite a reliable feature for separating them. There are 
intermediate shades of color between the lightest and the darkest, but as 
a general thing specimens of the same species have a uniform shade. As 
a rule, all the species of Actinocrinus, Platycrinus, Graphiocrinus, Scaphiocrinus, 
Tarocrinus and the Blastoids, are of light color; Dorycrinus and Dichocrinus 
