682 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



Remarks. — Described from the basals and radials, all the other parts 

 being unknown. The interbasal sutures, which are represented in both of 

 Miller's figures, are not visible in the specimens ; but the places where they 

 should be are indicated by elevated ridges. 



Platycrinus niotensis M. and W. 

 Plate LXXI. Fig. 9. 



1865. Meek and Worthen ; Proceed. Acad. Nat. Sci. Phila., p. 162 ; and Gaol. Rep. Illmois, Vol. HI. 



p. 513, Fig. 3. 

 1881. W. and Sp. ; Revision, Part II., p. 73 (Proceed. Acad. Nat. Sci. Pliila., p. 2i7). 



A very small species. Calyx below the summit of the radials cup- 

 shaped, the .sides distinctly rounded in the type, scarcely convex in other 

 specimens ; the base short, basin-shaped, broadly truncated at the bottom. 

 Plates smooth and slightly convex, the basi-radial and interradial sutures 

 distinct, but not grooved. 



Basals forming a short cup of one third the height of the radials, the 

 lower rim somewhat projecting outward, the lateral margins of the plates 

 slightly raised toward the suture lines, and forming indistinct ridges and a 

 small projection at the lower extremity of each suture. Radials large, as 

 long as wide, or a little longer, widening moderately from below upwards ; 

 subquadrangular, the superior angle slightly truncated by the interradial 

 plates. Facets shallow, and occupying about half the width of the plates. 

 Costals trigonal, rounded at the lower end, completely filling the facets. Dis- 

 tichals two, both one third wider than long. Arms four to the ray, rather 

 heavy throughout, and biserial from the second or third plate. Column near 

 the base compressed and tortuous, being composed of alternate thick and 

 thin elliptic joints. 



Horizon and Locality. — Keokuk group ; Niota, 111., Indian creek and 

 Canton, Ind. 



Ti/2}& in the Illinois State collection. 



Bemarlis. — The figure of the type specimen in the Illinois Eeport is 

 somewhat misleading ; the base is made too high and the radials too short. 

 It also appears as if one of the rays had but three arms, while it actually has 

 four, like the other rays. The species is closely allied to F. Sarce, but is 

 considerably smaller, and its arms less numerous and proportionally stronger. 

 It resembles still closer F. ionoensis, but that has five to six arms to the ray, 

 and the arms are shorter. 



