PALEONTOLOGY OF IOWA. 557 



pentagonal, smaller than the first radials, supporting two 

 smaller interradials of the second series, except on the anal 

 side, where the first interradial is hexagonal, and supports 

 three plates in the second range. Third series of interradials 

 two, and supporting a fourth series of two very narrow 

 plates' enclosed between the brachial plates. Brachial plates 

 two, resting in part on the upper sloping edges of the third 

 radials and the edges of the adjacent interradials, except on 

 the anal side, where the arrangement is modified by the 

 larger number of plates. Brachial plates indented on their 

 upper edges, the articulating scar reaching nearly to their 

 base. Arms unknown. Surface finely granulate. Column small. 



This, so far as I am aware, is the first species of this genus found in the country, 

 and I take pleasure in dedicating it to the discoverer. 



Fig. 8 a. View of anal side. 



Fig. 8 b. Basal view of same specimen. 



Fig. 8 c. Enlargement, showing more distinctly the form and arrangement of 

 the plates. 



The diagram used for the generic illustration above is of this species. 



Geological formation and locality. In the Burlington limestone : Bur- 

 lington, Iowa. 



GENUS ICHTHYOCRINUS ( CONRAD). 



GENERIC FORMULA. 



Basal plates, 5. 

 Radials, 3X5. 

 Arms 10, which are frequently bifurcated. 



THE basal plates are small, and sometimes entirely hidden 

 by the column, and there are sometimes three other rudi- 

 mentary plates within the five basal plates. 



Ichthyocrinus Irarlingtonensis ( n. s.). 



BASE regularly and broadly convex : column small. Basal 

 plates very minute, showing a triangular form beyond the 

 margin of the column. First radial plates very irregularly 



