310 PALAEONTOLOGY OP ILLINOIS. 



Column rather slender, and composed of short, round, even joints. 

 Position and locality: Upper beds of Keokuk limestone, Hamil- 

 ton, 111. 

 No. 174 of Mr. L. A. Cox's collection. 



NOTE. After publishing a description of this form in 1882, 1 ascertained that the error 

 in its diagnosis, as published in the Boston Journal of Natural History, was due to a 

 typographical error, and therefore restore the name adopted by Hall in 1801. 



CYATHOCRINUS MABSHALLENSIS, Worthen. 



PI. XXX. Fig. 4. 



Cyathocrinus MarshaUensis, WORTHEN, February, 1882. 



Bulletin No. 1, of the Illinois State Museum of Natural History, p. 33. 



Diagnosis: Body mamillate, length and breadth about equal, and 

 truncated at the base where it joins the column. Basal plates small, 

 longest on the anterior side, angular above, and forming by them- 

 selves a shallow pentagonal cup. Subradials about as high as wide, 

 four of them of equal size and hexagonal, the fifth on the anterior 

 side nearly twice as large as the others and heptagonal. The radials 

 on four of the rays are about the same size as the smallest subra- 

 dials, pentagonal in form, their lower angles fitting into depressions 

 between the subradials, constricted from the lower lateral angles 

 upward, so that the upper margins, which support the brachials, are 

 only about half as wide as the greatest width below. 



Brachials three on these four rays, narrower than the radials, two 

 of them quadrangular, and the third angular above, supporting the 

 first divisions of the arms. The lateral spaces between the brach- 

 ials, and extending below to the middle of the radials, appears to 

 have been filled by a calcareous integument, or with minute plates 

 that are too small to present definite forms under an ordinary glass. 



On the anterior side of the specimen, the large anterior subradial 

 is succeeded by a quadrangular radial resting directly upon its trun- 

 cated upper margin, and this is succeeded by two or more quad- 

 rangular brachials, beyond which its structure cannot be made out. 



The arms after the first bifurcation on the third brachial, divide 

 again on the sixth or seventh plate, and some of the branches once 

 or twice more, higher up. They are composed of rather long, rounded 

 quadrangular joints, decreasing gradually in size to their extremi- 

 ties. Anal plates unknown. 



