no 



■normal condition, may never luivo had more than two. While 

 we have two specimens of this species this particular ray hap- 

 pens to be wholly preserved in only one of them. Third 

 primary radials, in the four rays, a little larger than the sec- 

 ond, thi-ee of them pentagonal, and the one on the right of 

 the azygous area hexagonal, as shown in both of oiw speci- 

 mens; all are axillary, and support on each upper sloping side 

 a single secondary radial, which is axillary and supports upon 

 each superior sloping side a single tertiary radial, except in 

 the ray on the left of the azygous area, where there are two 

 tertiary radials. This peculiarity in the ray having only two 

 primary radials does not appear to be abnormal, and certainly 

 is not the result of any mechanical injury. There are, there- 

 fore, twenty ambulacral openings to the vault. 



In one of the regular interradial areas adjacent to the ray 

 opposite the azygous area there are six plates, one of which 

 connects with the plates of the vault, and in the othe-r area 

 there are seven plates, one of which connects with the plates 

 of the vault. In the other two regular areas there are onlv 

 five plates, neither of which reaches the plates of the vault, 

 becau.se the areas are cut off by the union of the tertiary ra- 

 dials. The azygous area contains nine plates. Tic first one 

 is in line witli the first primary radials and somewhat sm.allcr; 

 it is followed by two plates in the second range, five plr.tes in 

 the third range, and only one in the fourth range which is 

 cut off from the vaull by the union of the tertiary radials 

 above it. 



Vault very convex and having more ca]iacity than the calyx. 

 It is covered by large, polygonal, spiniform plates. The- vault 

 is injured at the summit in both of our specimens .so the char- 

 acter of the probo.scis cannot be determined. No ovarian pores 

 discovered. 



This species, in some respects, resembl<>s a Bdiocrinus. but 

 the hexagonal, second primary radials must ])la('e it in ihe 

 genus Acii'nocrimi!'. The fact that the azygous ai'ea and the 

 two interradial areas adjoining do not connect with the vault, 

 while the other two interradial areas do. would seem to be of 

 specific importance, without reference to the want of unifoi'niity 

 in the number of plates, in the ditteront areas. The ray on 



