45 



The basal plates are substantially covered by the end of the 

 column. The first primary radials are rather large, slightly 

 unequal in size, directed from the column nearly horizontally, 

 and those abutting on a single basal plate are hexagonal and 

 those abutting upon two basals are heptagonal. The second 

 primary radials are hexagonal, differ in size and are about as 

 large as the first. The third primary radials are smaller than 

 the first or second, three are pentagonal and two are hexa- 

 gonal. They are axillary and bear the secondary radials. Two 

 of the lateral rays have no tertiary radials and therefore have 

 only two arms each. The ray on the left of the azygous area 

 has four arms; the ray on the right of the azygous area has 

 three arms and the ray opposite the azygous area has three 

 arms. This arrangement gives to the species fourteen arms. 



In the regular interradial areas there is one hexagonal plate 

 separating the second primary radials, and two plates in the 

 second range separating the third primary radials, each of 

 which is about the size of the primary radials; above these 

 plates the sutures are not distinct, The azygous area is large 

 and protuberant, at the third and fourth ranges of plates. 

 The first azygous plate is in line with the first primary radials 

 and nearly as large; it is followed by three plates in the sec- 

 ond range and by five plates in the third range, all of which 

 are subequal in size; above these plates the sutures are not 

 distinct in our specimen, but there seems to be five plates in 

 the fourth range. 



The vault is only moderately convex over the ambulacral 

 areas, and rather slarply depressed toward the margin in the 

 interambulacral areas. There is a tumid plate in the center 

 and an azygous opening adjoining it. The sutures are de- 

 stroyed in our specimen. There are no spinous plates over 

 the ambulacral canals. This species is distinguished by its 

 general form and fourteen arms. 



Found in the Hamilton Group, in Clarke county, Indiana, 

 and now in the collection of Mr. J. F. Hammell. 



