May, 191/ j Silurian Fossils from Ohio 243 



From the Cedarville dolomite, at the eastern Mills quarry, 

 one mile southwest of Springfield, Ohio. 



The tegmen of the specimen from Springfield, Ohio, here 

 described, is not preserved. This prevents the elucidation of 

 the following anomalous structure. Apparently an anal tube 

 extends from the upper margin of the right posterior inter- 

 brachial area diagonally upward and toward the left. Possibly 

 the right side of the tegmen was crushed in and a part of the 

 anal tube preserved in such a position as to give the present 

 misleading appearance. 



The specimen here described differs from Ilabrocrinus 

 ornatus. Hall and Whitfield, from the Cedarville dolomite at 

 Yellow Springs, Ohio, in several important particulars. The 

 form of the dorsal cup is more obovate-globose, and the arrange- 

 ment of the plates in the anal interradial area is different. 



In Ilabrocrinus ornatus, Hall and Whitfield, the first anal 

 plate supports a transverse set of three plates whose upper 

 margins are sufficiently near the same level to cause the next 

 set, consisting of five instead of three plates, also to form a 

 transverse row. The latter is followed by another transverse 

 row consisting also of five subequal plates, and the latter are 

 followed by five plates of smaller size, beyond which extend the 

 basal plates of the anal tube. 



In Habrocrinus benedicti, Miller, from the Laurel limestone at 

 St. Paul, Indiana, the first anal plate supports a transverse set of 

 three plates, followed by a transverse set of five plates of which 

 the middle and two end plates occupy a distinctly higher posi- 

 tion, and the latter are followed by two additional zigzagging 

 sets of five plates. At the bases of the free arms the upper 

 margin of the dorsal cup projects outward. The same general 

 form and arrangement of plates is found in Ilabrocrinus chicago- 

 ensis, Weller, from the Racine of Bridgeport and Joliet, Illinois. 



In Habrocrinus howardi, Miller, the first plate of the anal 

 interradial area is followed by two sets of transverse plates of 

 plates each, and these by a transverse set of five plates which 

 are not in line; but the middle three plates of the last set are 

 not conspicuously smaller than the end plates, the base of the 

 calyx is truncated, and the upper part of the dorsal cup projects 

 strongly at the bases of the free arms. 



