53 



of the azygous area is small and hexagonal, the others are pentag- 

 oual or hexagonal, axillary, and support, on each upper sloping 

 side, two secondary radials, the last being axillary, and support- 

 ing, upon each upper sloping side, two tertiary radials, except on 

 each side adjoining the azygous area, where there is only a single 

 secondary radial, which is axillary, and bears upon each superior 

 sloping side three tertiary radials, which arrangement gives to each 

 ray four ambulacral openings to the vault. There are, therefore, 

 twenty arms and twenty ambulacral openings to the vault in this 

 species. 



The regular iuterradial areas are widely separated from the 

 plates of the vault, and in the areas that can be determined in 

 our specimen there are three plates, one, followed by two small 

 ones in the second range. In the azygous area there are seven 

 nodose plates. The first one is in line with the first primary ra- 

 dials and larger than either of them. It is followed by three 

 plates in the second range, two in the Ihird range, and one in 

 the fourth range that unites with an elongated plate belonging to 

 the vault. 



The vault is highly convex or conoidal and has a capacity fully 

 eqaal to that of the calyx. It is covered with very tumid and 

 nodose plates, and bears a very large central proboscis. 



This species is readily distinguished by its form and nodose 

 plates from all othei's that have been described, among the twen- 

 ty-armed species. Probably it is as near B. honorabilis as any 

 other, but there are more tertiary radials in that species than in 

 this one, and the ambulacral openings are directed upward instead 

 of horizontally. The iuterradial areas are more elongated and 

 have more ranges of plates than there are in this species, and 

 the azygous area is is not connected with the vault in that spe- 

 cies as it is in this. The vault is much more conoidal in this 

 species than in that, and has a much larger proboscis. The two 

 species are so dissimilar that they are readily distinguished. 



Found in the Keokuk Group, on Little Barren river, Kentucky, 

 and now in the collection of (Jharles L. Faber. 



