])late, less than one fourth as large, in the second range. 

 There is one small plate in the thii-d range, that unites witli 

 two plates belonging to the vault. 



The vault is quite evenly convex, has small ridge.s over the 

 ambulacral canals and bears a small, short, almost central 

 proboscis. The sutures cannot be distinguished, in our speci- 

 men, and the surface is eroded so the ornamentation is not 

 shown, in the illustrations. There are four ovarian apertures 

 to each ray, or twenty in the the species, all of which are 

 elongated and enter the vault instead of the ambulacral canals. 



This species in its general form resembles D. oplaitif, but 

 that species has fifteen arms while this one has thirteen so 

 the arm formula alone will distinguish them. The only species 

 with which this one agrees, in the arm formula, is D. lyoni 

 above described but the species are readily distinguished by 

 the general form and surface ornamentation as well as by the 

 interradials. It is not necessary to make any comparison with 

 any other species. 



Found by J. P. Hammell in the Hamilton Group, near 

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

 Gurley. 



nOLATOC'RINUS PECUI.IAUIS, U. Sp. 



Plate III, Fig, 28, azygous side; Fig. 29, basal view; Fig. 30, 



summit. 



Species above medium size but very short. Calyx broadly 

 and deeply concave below and slightly constricted below the 

 arras. Radial ridges very inconspicuous, and interrupted at 

 the sutures. 



The ])lates ai-e very tumid and radiately furrowed toward 

 the margins. The surface ornamentation resembles that of D. 

 vasculum and there is much resemblance in the general form 

 of the two species, but that is an eighteenarmed species and 

 this is a .seventeeia armed one. Column small but having a 

 comparatively large cinquefoil canal. 



Basals deeply sunken in the concavit;- .so as to extend higher 

 than the base of the arms. The hollow cone thus formed is 

 not entirely filled by the end of the column and the basal disc 

 may be seen having a diameter one-half greater than the 



