80 



specimen apparently of the same species, a third branch is given 

 off from the third plate above the first division, making six arms to 

 these two rays. 



From four to six interradials can be seen, the first of which is 

 larger than the others, but owing to the crushed condition of the 

 specimens, the exact form and number of these plates cannot be 

 determined. 



Column round, rather stout, and composed of alternately thin and 

 thicker joints. 



The specimen showing six arms to the ray, also shows a marked 

 prominence in the central portion of the body plates, which is not 

 seen in the other, and this we take as the type of li. Coxanus, and if 

 these differences should be regarded as of specific importance the 

 name R. polydacti/lus might be used to designate the other variety. 



Position and locality : Upper part of the geode bed, one mile be- 

 low Keokuk. 



Nos. 197 and 223 of Mr. L. A. Cox's collection. 



PLATYCRINUS MONROENSIS. N. SP. 



Body small, cup-shaped, about once and a half as wide as high. 

 Basal plates extending about one half their length beyond the first 

 columnar joints, the lower margin projecting so as to form a narrow 

 rim to the base. Eadials wider than high, the articulating scar 

 occupying only about one-third to one-half of their entire width. 



Brachials single, narrow, subtriangular, sharply cuneate above, 

 and supporting on their upper sides the first arm plates. On the 

 two rays visible in the specimen, under examination, the arms, after 

 their first division on the brachials divide again, both divisions once 

 on the second plate above the brachials, and one of them the second 

 time on the second arm-plate above, giving five arms to each ray. 



Arms composed at first of long, rounded joints, that are somewhat 

 zigzag, and projecting on their margins, where they give off strong 

 pinnules, but towards their extremities they are composed of short, 

 triangular pieces that also sustain pinnules on their longest margins. 

 Pinnules quite stout, their diameter being about equal to one-third 

 of the widtii of the plates to which they are attached. 



Position and locality : St. Louis limestone, Monroe county, 111., 

 and Blount county, Tenn. 



Illinois State collection. 



ERETMOCRINUS VARSOUVIENSIS. N. SP. 



Body small and turbinate below the base of the arms. Basals 

 short, slightly projecting on their lower margins, forming a well de- 

 fined rim around the base. 



Primary radials three, the first comparatively large, hexagonal or 

 heptagonal, the succeeding ones small, one quadrangular and the 

 other subtriangular, supporting on its upper angles tlie secondary 

 radial series. 



