16 



tagonal, larsor than tho second, wider than high, greatest width 

 below tlie middle, at tho angle.s formed by the junction of the 

 lower expanding and upper sloping sides, axillary, and sup- 

 porting on each upper sloping side the secondary radials. In 

 the ray on the right of the azygous area, and in each lateral 

 ray, there are two .secondary radials, the second one of which 

 is axillary, and bears upon each superior side two tertiary ra- 

 dials. which gives four arms to each of these three rays. In 

 tho ray on the left of the azygous area, there are two secondary 

 radials, in the proximal series, the second one of which is ax- 

 illary, and bears upon the proximal side two tertiary radials, 

 and on the distal side one large tertiary radial, and in the dis- 

 tal series there are two secondary radials only, the last one 

 being quite large. This gives to this ray three arms. In the 

 ray opposite the azygous area the third primary radial bears 

 upon each su2)erior sloping side three secondary radials, which 

 gives to this ray two arms. There are, therefore, .seventeen 

 arm openings to the vault in tliis species. 



In the regular intcrradial area, between the three and four 

 armed rays, there are only three jjlates, one very large fol- 

 lowed by two elongated plates, one of which extends higher 

 than the other. In each of th(^ other three regular interradial 

 areas ohero are four plates, one large plate, followed by two 

 in the second range and one in the third. The azygous area 

 is subovate in outline and contains nine plates. The first one 

 is in line witli tlu' first i-adials, l>ut smaller and narrower; it 

 is followed by three much lai-ger plates in the second range, 

 !ind these by three in the third range, which are suj ported 

 on two of the plates of the second range. Above the middle 

 one in the third range there is a small plate, and between its 

 i-iglit siii)erior sloping side and the left su])(>rior side of the 

 ii])p(u- j)late, in the third range, an elongated plate is sup- 

 ported that extends its superior angle between the .second ter- 

 tiary radials and unites with the plates of the vault. 



Vault conoidal, slightly dejjressed in the interradial areas, 

 and covei-ed with rather large, polygonal, convex jjlates. Two 

 small ovai-ian {'^} a])c:tiires may be distinguished between the 

 anibulacral openings in the azygous area; they arc above the 



