62 



and support upon the upper sloping sides the tertiary radials. 

 The tertiary radials vary from four to ten in the different 

 series, and the arms are not of equal size. The last tertiary 

 radials, in each series, are axillary and support the quater- 

 nary radials. The distal rays again divide, which gives to 

 each ray twelve arms. There are, therefore, sixty arms that 

 infold upon the summit of this species. 



The interradial areas are depressed, narrow, elongated, and 

 differ in size and number of plates. The plates graduate into 

 those of the vault without any distinct line of separation. The 

 first plate rests between the superior sloping sides of the first 

 primary radials, and is more or less elongated. It is followed 

 by two plates in the second range, but these are more elon- 

 gated in some areas than in others, and they differ in size. 

 There are three plates in the third range and above these the 

 plates curve over toward the vault, in the central part of the 

 areas, while uniting at the sides with the secondary radials. 

 A small inter secondary plate may be seen in some of the 

 areas directed inward while it evidently unites with the plates 

 of the vault. The azygous area is narrow, the first plate 

 truncates a subradial and supports a series of rounded plates, 

 on each side of which, smaller plates connect it with the pri- 

 mary radial series. 



This species is distinguished by its column, expanding pri- 

 mary radial series, number of secondary and tertiary radials, 

 and by the narrow and elongated interradial areas. The pus- 

 tules on the surface are very large though not shown in the 

 illustrations. There is no described species for which it can 

 be mistaken by anyone competent to make a comparison. 



Found in the Keokuk Group, at Crawfordsville, Indiana, and 

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



Family PLATYCRINID^. 



PLATYCRINUS ILLINOISENSIS, n. sp. 



Plate V, Fig. 5, basal view of calyx; Fig. 6, side view of same; 

 Fig. 7, summit view of the calyx of a larger specimen. 



Species about medium size, though there is considerable dif- 

 ference in size among the specimens collected. Calyx bowl- 

 shaped, subpentagonal, broadly truncated below, sutures deeply 

 beveled, radials longitudinally convex. Surface smooth. Plates 

 thick. Column and arms unknown. 



