24 



pore on each side of each radial series may be plainly seen in the 

 larger specimen, but only part of them can he seen in the specimen 

 illustrated. 



Basals form a short round disc, having an hemispherical depres- 

 sion for the attachment of the column. First primary radials as 

 large as the second and third together, wider than Long, three 

 hexagonal, two heptagonal. Second primary radials quadrangular, 

 two or two and a half times as wide as long. Third primary radials 

 larger that the second, two hexagonal, three pentagonal, axillary, 

 and in the ray opposite the azygous area supports, on each upper 

 sloping side, three secondary radials, which gives to this ray two 

 arms. In one lateral ray the third radial bears two secondary radials 

 on each upper side, and in the other only one, the last being axillary 

 and supporting upon each upper side two tertiary radials. which 

 gives to each of these rays four arms. In the ray on each side of 

 the azygous area the third primary radial supports, on the distal 

 side, three secondary radials. and on one of the proximal sides one 

 axillary secondary radial, which bears on each side two tertiary 

 radials and on the other proximal side two secondary radials. the 

 last being axillary and supporting on each upper side two tertiary 

 radials. which gives to each of these rays three arms. There are, 

 therefore, sixteen ambulacral openings to the vault in this species. 

 The arm formula is 3-j-4-|-2-|-4-f-3. 



There are three plates in each regular iuterradial area, one, fol- 

 lowed by two. which are cut off from all connection with the vault 

 by the union of the radials above them. There are only four plates 

 in the azygous area. The first one is in line with the first primary 

 radials and about the same size. It is followed by three plates, the 

 middle one being quite large, but cutoff from the vault by the union 

 of the tertiary radials above it. 



The vault is nearly as large as the calyx and bears a small central 

 proboscis. It is covered with convex, polygonal plates and is slight!} 7 

 lobed over the ambulacral canals. 



It is a marked species in its general appearance and need not be 

 compared with any other sixteen-armed species to distinguish it. 



Found by R. A. Blair, in the Burlington group, near Sharon, in 

 Southwestern Missouri, and now in the collection of S. A. Miller. 



