Carboniferous Rocks of the Mississippi Valley. 275 



above, supporting on each upper face a small supra-radial, 

 which sustains on the outer face a series of brachial plates, 

 and on the inner face a supra-radial plate of the second 

 order ; this supports a brachial plate on its inner face, and 

 apparently a supra-radial of the third order on the outer 

 face. (There may be still other supra-radial plates not 

 seen in the specimen.) 



First interradial plate less than half as large as the first 

 radial plate, hexagonal or heptagonal, supporting two small 

 plates in the second series, and one in the third. Anal 

 plates undetermined. 



Surface of plates marked by strong transverse nodes on 

 the radial series, and rounded nodes on the interradial 

 plates, connected across the sutures by strong angular or 

 rounded ridges. The basal plates, in addition to the form 

 of the base and projecting angles, are margined on each 

 lateral face by a strong ridge, with a corresponding ridge 

 down the centre, dividing it into two areas which stand 

 obliquely to each other, and have a low rounded node in 

 the centre of each one. The plates of the dome and those 

 of the proboscis for some distance above its base are 

 marked by long, strong, curved spines; the proboscis in 

 the middle and upper parts is composed of very short, 

 wide plates, marked by transverse ridges, giving a crowd- 

 ed, wrinkled aspect to the surface. Column composed of 

 round plates ; every fourth or fifth, and near the top every 

 second or third plate, is much larger, and marked at inter- 

 vals by strong nodes, which give it a general pentangular 

 form in the upper portions. 



Geological formation and locality. Burlington lime- 

 stone, Burlington, Iowa. Collection of B. J. Hall. 



Actinocrinus chloris (n. s.). Body below the arms 

 broadly urn-form, base truncate ; dome conical, and some- 

 what lobed in its lower part. Basal plates with the lower 

 margin projecting in a thin, denticulate rim, short, at least 



