INDIf\Nf^ Pf\Lf\&ONTObOGY. 



separate the last radials and unite with the plates of the vault. These plates 

 are also more or less nodose. 



The azygous area is well marked in this species by being wider than either 

 of the other areas, and having the plates more nodose and deeper sculptured. 

 The nodes on the adjacent radial series, disconnected with the radial ridges, 

 are more prominent in this area than in either of the others, and form a con- 

 spicuous circle around the first azygous plate. The number of plates in the 

 azygous area is the same as in each of the other areas. 



The vault is depressed conical, though as seen from above the outline is 

 sub-pentagonal. There is a small, short, sub-central proboscis. Each plate 

 over the junction of the ambulacral canals bears a spine having a length about 

 twice its diameter, and each plate surrounding the base of the proboscis, bears 

 a similar spine. Each of the other plates on the vault bears a few small nodes. 

 There are twenty ovarian pores, four to each radial series, that penetrate the 

 plates at the base of the arms and not the vault between the arms as in many 

 species. 



This species most resembles D venustus, with which it agrees in the num- 

 ber of ambulachral openings to the vault. It will be most readily distinguished 

 by having comparatively a shorter calyx, which is due to the fact that there is 

 one less plate in each tertiary radial series, and one less in each of two of the 

 secondary radial series, in all making twenty plates less in the calyx of this 

 species than are in D venustus- The interradials in that species being neces- 

 sarily proportionally longer than they are in this. The vaults and vault plates 

 are also different in the two species. The surface ornamentation may also be 

 sufficient in well preserved specimens to distinguish the species, but as there is 

 some resemblance in this respect, probably it cannot be relied upon for a dis- 

 tinguishing feature. It is to be presumed that D- venustus possessed the same 

 number of ovarian pores, probably arranged higher up on the plates, at the 

 base of the arms, and so clpsely connected with the ambulacral openings that 

 they were not distinguished by me when describing that species. Tiiere is no 

 difficulty in distinguishing the ovarian pores in this species. 



Found by G. K. Greene, in the Hamilton Group, near Charlestown, Ind., 

 and now in his collection. 



