38 



each upper sloping side a single secondary radial which is axillary, 

 and one of them bears upon each upper sloping side three tertiary 

 radials and the other bears upon one sloping side three tertiary radials 

 and upon the other, two, the last of which is axillary and bears upon 

 each upper side two quaternary radials, which gives to this ray five 

 arms. There are, therefore, seventeen arms in this species. The 

 arm formula is 3 +5 3 3 3. 



There seem to be only two interradials in each area. The first is 

 medium, in size, for species, in this genus, and the second is smaller 

 and cut off from connection with the vault by a union of the radial 

 plates. Or, at least, we cannot find any sutures for the small plates 

 that usually unite these areas with the vault. The azygous area is 

 substantially like the other areas. 



The vault is highly convex and bears a short subcentral proboscis. 



The vault is covered by a few large, plane plates. There are two 



elongated, curved, ovarian apertures in each interradial area, and 



two within each radial series which gives to this species twenty 

 ovarian apertures. 



This species most resembles D. hammelli, from which it is 

 distinguished by having seventeen instead of sixteen arms. It has 

 also an increased number of tertiary plates as well as the quaternary 

 plates. The interradial areas are connected with the vault by two 

 relates in that species, which do not, as it appears, exist in this 

 species. There are other minor differences. 



Found by Geo. K. Greene in the Hamilton Group near Charles- 

 town, Indiana, and now in the collection of Wm. F. E. Gurley. 



STEHEOCEINUS INDIAN ENS IS n. Sp. 



Plate I II, Fig. 13, view of a calyx showing all the plates ; Fig. 

 11. lateral view\ shaming height of calyx; Fig. 15) view 

 of a silicified specimen in the usual condition. 



Species small. Calyx flat with the exception of raised, rounded, 

 radial ridges. The surface of the plates is delicately sculptured. 



The basal plates are small, and form a small, more or less, conical 

 elevation in the interior. The first primary radials are about twice 

 as large as the second. The second are axillary and support on each 

 upper sloping side a series of secondary radials. As many as five 

 secondary radials are preserved in some of the rays. There is no 

 other bifurcation of a ray. There are, therefore, only ten arms in 

 this species. The first regular interradial plate is elongated and has 



