54 



Third primary radials expand to the superior lateral angles, lon- 

 ger than the second, wider than high, pentagonal, axillarj^ and 

 bear upon each siiperior sloping side in three of the rays a sin- 

 gle secondary radial, which is axillary and bears upon each upper 

 sloping side four tertiary radials. This gives to each of these rays 

 four arms. In the two rays opposite the azygous area on one of 

 the superior sides of each of the third primary radials there are 

 four secondary radials, and on the other a single secondary radial, 

 which is axillary and bears upon each upper sloping side four 

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

 There are, therefore, eighteen arms in this species and eighteen 

 ambulacral openings to the vault. 



The first interradial is very large, lias nine sides and is broadly 

 truncated for the second interradial. The second interradial is 

 less than half as large as the first. In three of the areas it is 

 followed by two plates in the third range and one in the fourth, 

 and in one of the areas, by a single plate in the third range and 

 two in the fourth. The azygous area is a little larger than the 

 others, has one plate in the first range, one in the second, three 

 in the third and two in the fourth. 



The vault is convex and moderately depressed in the interradial 

 areas. The sutures are not shown in our specimen, and part of 

 the vault is not preserved. There are two "ovarian apertures" be- 

 tween each of the arms which gives to the species thirty-six of 

 these orifices. Those in the interradial areas are evidently larger 

 than the others. 



This species is distinguished by its surface ornamentation, in- 

 terradial and azygous plates, and by having eighteen arms. These 

 characters will readily separate it from all others that have been 

 described. 



Found in the Hamilton Group, at Charlestowu, Indiana, and 

 now in the collection of Wm. F. E. Gurley. 



DOLATOC'RINUS EXOUNATDS, n. sp. 



Plate V, Fig. 10, basnl view: Fig. 11, aziigous side on the left; 

 Fig- 12, summit viexo. 



Species below medium size. Calyx truncated below and expand- 

 ing to the arm, giving it a bowl shape. Kadial ridges rounded 

 and composed almost wholly of elongated nodes in tlie central 

 part of the plates. The surface of the plates is radiately sculp- 



