RHODOCRINID^. 227 



strong, contiguous ; composed of elongate joints. Interradial spaces arranged 

 in four rows. The plates interposed between the radials smaller than these ; 

 followed bj 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., 

 Iowa. 



Ti/pes 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 purphsh 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, Plati/crinus, Grapliiocrinus, ScapMocrinus, 

 Taxocrinus and the Blastoids, are of light color ; Borycrinus and Dichocrinus 



