33 



ment of the column, and the top is one-half wider than the 

 diameter at the base. The plates are about twice as wide as high, 

 and the sutures are broadly beveled. A delicate angular ridge 

 extends from the bottom of each plate to the middle of each 

 side of the adjoing radials. First primary radials the largest 

 plates in the calyx, a little wider than long, three hexagonal, 

 two heptagonal. The central node is high, transverse, and 

 from it a delicate angular ridge radiates to the middle of each 

 side of each adjoining plate. When viewed from below these 

 high, transverse nodes obscure the view of the plates above. 

 Second primary radials about half as large as the first and or- 

 namented in the same way. The one on the left of the azy- 

 gous area is pentagonal, the others are hexagonal. The third 

 primary radials are smaller than the second and ornamented 

 in the same way. Three are hexagonal, one heptagonal and 

 one pentagnal. The heptagonal plate and one of the hexago- 

 nal plates are truncated, at the summit, by an inter- secondary 

 plate. In the other areas the inter- secondary plates do not 

 abut upon the third primary radials. They are axillary and 

 support on each superir lateral side a single secondary radial, 

 which is ornamented like the radials below, and is axillary and 

 supports on each upper sloping side a single tertiary radial. 

 The tertiary radials are also ornamented like the radials. 

 This is a feature common to every plate in the calyx, except 

 the nodes become more pointed and less transversely elongated 

 as they approach the free arms. There are, therefore, twenty 

 arms and twenty ambulacral openings to the vault in this 

 species. 



All the interradial and intersecondary areas connect their 

 plates with the plates of the vault. In the intersecondary 

 areas there are two narrow plates, one following the other, the 

 last one extending to the vault. The number of regular inter- 

 radials varies in the different areas from five to seven. In an 

 area having five plates there is one plate in the first range, 

 two in the second, one in the third and one in the fourth. In 

 another area having six plates, there are two plates in the 

 third range, and in an area having seven plates, there are two 

 plates in the third range and two in the fourth range. In the 

 azygous area there are nine plates. The first one is in line 

 with the first primary radials and about as large. It is fol- 

 lowed by two plates in the second range, two in the third 

 —5 



