56 



diameter of the column. First primary radials as long as wide 

 and entirely within the basal concavity and forming part of the 

 funnel shaped depression. Second primary radials form part 

 of the basal concavity, a little wider than long, quadrangular 

 and the calyx will rest on the central nodes of the first inter- 

 radials and these plates. Third primary radials curve upward, 

 nearly as long as wide, pentagonal, axillary, and in the ray on 

 each side of the azygous area, bear upon each upper sloping 

 side a single secondary radial which is axillary and bears upon 

 each upper side two tertiary radials, which gives to each of 

 these rays four arms. In each of the other three rays the 

 third primary radial bears upon one upper sloping side three 

 secondary radials, and upon the other one secondary radial, 

 which is axillary and supports upon each upper sloping side 

 two tertiary radials, which gives to each of these three rays 

 three arms. There are, therefore, seventeen arms and seven- 

 teen ambulacral openings to the vault in this species. It will 

 be observed that the arm formula is the same that is found in 

 D. bellulus. 



The interradial areas are not alike, in this species, and the 

 azygous area is smaller than either of three of the others. 

 The first interradials are the largest plates in the calyx, the 

 lower half of each bends into the basal concavity from the 

 middle part and upward at the superior end. In the azygous 

 area and in one of the other areas, it is followed by a single 

 plate, in the second range, about one-fourth as large, and it is 

 followed, in the third range by a smaller plate that unites 

 with the plates of the vault. In the other areas the second 

 interradial is smaller and is followed by two plates in the third 

 range and these are followed by a single plate in the fourth 

 range that unites with the plates of the vault. The plates in 

 the interradial areas thus vary from three to five. 



The vault is only moderately convex, depressed in the inter- 

 ambulacral areas, and covered with large tubercular plates. 

 The sutures between the plates are not shown, in the illustra- 

 tions, because only part of them can be distinguished, in our 

 specimen. The proboscis or short tube for the azygous orifice 

 is excentric, from the azygous side, which is a peculiarity not 

 often observed among the crinoids. There is a large central 



