32 



Basals small but extending beyond the column and forming 

 a low cup that is visible in a side view. Subradials rather large 

 and about as wide as high. First radials a little wider than 

 long, pentagonal, truncated the entire width above and sepa- 

 rated from the second radials or brachials by a slightly gaping 

 suture. A single, elongated brachial or second radial, rounded 

 and contracted in the middle, and axillary, in four of the rays, 

 supports upon its upper sloping sides the free arms. In the 

 ray on the right of the azygous area the first brachial or sec- 

 ond radial is a subquadrate plate that supports the second 

 brachial or third radial, which is rounded, and axillary, and 

 supports upon its upper sloping sides the free arms. The arms 

 are long, slender, and fit compactly together and are composed 

 of a single series of cuneiform plates. The arms do not bifur- 

 cate and there are, therefore, only ten arms in this species. 

 Pinnules are not large and are arranged on the inner part of the 

 arms so as not to prevent the arms from fitting compactly to- 

 gether. 



The azygous plates alternate, as is usual in this genus The 

 first plate is the largest, which is an unusual feature, and rests 

 upon the upper sloping sides of two subradials, separates the 

 first radial on the right from the second azygous place and is 

 truncated above by the third azygous plate. The second plate 

 is somewhat smaller than the first, hexagonal and only slightly 

 truncates a subradial. It abuts upon the first radial and part 

 of the second radial or brachial on the left. Above it the 

 plates alternate and become rapidly smaller. 



This species is distinguished by its general form, slender 

 arms, and by having a single brachial in four of the rays and 

 two brachials in the ray on the right of the azygous area. 

 This last feature shows that Poieriocrinus cannot be divided 

 into subgenera based on the presence of one or two brachials 

 in the rays. 



Found in the Keokuk Group, at Boonville, Missouri, and now 

 in the collection of Wm. F. E. Gurley. 



