17 



and only a small part at the lower end is curved into the col- 

 umnar cavity. Strong radial ridges rise on the first radials, cross 

 the second and terminate at a tubercle on the third radials, from 

 which a delicate ridge crosses each secondary radial. The radial 

 ridges are most prominent in the central part of the plates. The 

 radiating lines from the commencement of the radiating ridges 

 form a pentagonal figure arour.d the small columnar cavity. Sec- 

 ond primary radials quadrangular and wider than long. Third 

 primary radials larger than the second, wider than high, pentago- 

 nal and support on each upper sloping side two secondary radials. 



First secondary radials about as large as the third primary radials 

 and hexagonal, except in some instances, where slightly truncated 

 by a small plate resting between the upper lateral side of the sec- 

 ond interradial and the base of the arm, they become heptagonal. 

 Second secondary radials much smaller; they separate the arms 

 and extend to the summit of the calyx and slope laterally. There 

 are ten arms, composed, at their origin, of a double series of 

 plates. No intersecondary radials. 



The first interradials are the larger plates of the body and have 

 nine sides. The second interradials are less than half as large as 

 the first and hexagonal; the three superior sides are the shorter 

 ones; the upper truncated side extends to the summit of the calyx 

 and a small vault plate abuts laterally against it. A small plate 

 rests between each superior lateral side and the second secondary 

 radial and forms part of the support of the free arm. There is no 

 azygous area. 



The vault is only slightly convex and very much depressed in 

 the interradial areas, especially between the arm bases. It bears 

 a small subcentral proboscis that is not preserved in our speci- 

 mens. It is covered with rather large, polygonal, tuberculated 

 plates, two of which, in each depressed interradial space, are elon- 

 gated, and the larger plates of the vault. There are no pores or 

 passages that penetrate the vault between the arms. 



Found in the Hamilton Group, near Charleston, Indiana, and 

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



—3 G. 



