PALAEONTOLOGY OF IOWA. 631 



FIG. 103. 



The illustration shows the third or last radial 

 ( the species being remarkable for possessing three 

 radial plates only) of one of the rays, with the 

 secondaries and interaxillary plates, and also the 

 bases of the arms to the third bifurcation. 



\J 



In many instances there is no suture-line visible at the junction of the small 

 patelloid plate with the next above; while in others, the suture is clearly visible, 

 proving it a part of the structure. Had it been otherwise, this thin projecting plate, 

 so far overlapping the plate below, would have prevented all motion in a direction 

 outwards; and since this structure extended into the arms, we should expect to find 

 there the means of free movement among the plates. 



All the species of FORBESIOCIUN'US appear to have been furnished with round 

 columns, composed near the body of thin equal joints; the whole tapering somewhat 

 rapidly, and becoming much attenuated and long-jointed below. 



Forbesiocrinus meeki ( n. s.). 



PLATE XVII. FIG. 3. 



BODY somewhat discoid, with strong marked rays. Basal 

 plates not developed beyond the circumference of the co- 

 lumn. Subradial plates minute. Radial plates large and 

 strong, more than twice as wide as long, scarcely indented 

 at their upper margins, the articulating faces deeply striated ; 

 the secondary plates, or those of the first division above the 

 radials, showing a shallow depression for the patelloid plate. 

 Interradial plates five or more : interaxillary plates two or 

 more ; anal plates unknown. 



COLUMN round, composed of thin equal joints, and tapering 

 rapidly from its summit downwards. 



Fig. 3. View of the base, showing the column, the subradial and radial plates, with 

 those of the first division of the rays, which in four of the rays are three 

 below the second bifurcation. 



Geological formation and locality. In the Keokuk limestone : Warsaw, 

 Illinois. 



