138 PROCEEDINGS OP THE ACADEMY OP [1886. 



Basals five, very large, long, narrow, of somewhat irregular 

 shape, forming an ovoid to cylindrical cup. The cup is nearl}^ 

 solid, having only a small central canal, and a shallow subconical 

 excavation at its upper end, the latter forming a part of the 

 viscei'al cavity. 



Radials five, always smaller than the basals, enclosing an anal 

 plate. They are subquadrangular, slightly excavated at their 

 upper side, and support four (exceptionally five) brachials, of 

 which the upper one is bifurcating and gives off the arms. Arms 

 two to each ray, simple throughout, composed of compound 

 joints, with one or two syzygies in each joint ; the upper segment 

 giving ofi" a strong pinnule. The oblique upper faces of the 

 epizjgal or pinnules-bearing joints are arranged alternately, and 

 this gives to the arms a strongly waving, zigzag outline. At the 

 extremities of the arm the pinnules are generally given off from 

 every joint. Pinnules long, arm-like, bifurcating once or twice, 

 like arms. With the arms the pinnules also correspond in length, 

 all of them extending to the same height. 



Anal plate resting between two of the radials and upon one of 

 the basals. This plate, which resembles the radials in form, sup- 

 ports a large ventral sac, composed of numerous hexagonal 

 plates, alternately arranged, with slit-like openings along their 

 lateral edges, which meet with corresponding slits in the adjoin- 

 ing plates. 



Other parts of the ventral side unknown. Column with or 

 without lateral cirrhi ; more or less sharply pentangular, the 

 outer angles radial, the rays of the central canal and the columnar 

 cirrhi directed interradially. 



Geological Position^ etc. Known only from the two divisions 

 of the Burlington limestone. 



1877. Belemnocrinus florifer W. and Sp., Amer. Journ. Sci. (Ser. 3), Vol. xiii, p. 



256. Upper Burlington limestone. Burlington, la. 

 1877. B. Pourtalesi W. and Sp., Amer. Journ. Sci. (Ser. 3), Vol. xiii, p. 258. Lower 



Burlington limest. Burlington, Iowa. 

 1862. B. typus White (type of the genus), Proc. Bost. Soc. Nat. Hist., Vol. ix, p. 



14. "W. and Sp , 1877, Amer. Journ. Sci. (Ser. 3), Vol. xiii, p. 254. Upper 



Burlington limest. Burlington, Iowa. 

 1866. B. Whitei Meek and Worthen, Acad. Nat. Sci. Phila., p. 251 ; also Geol. Rep. 



Illinois, iii, p. 463, PI. 18, figs. 4 a, h, c. Lower Burlington limest. Bur- 



lingtoD; Iowa. 



