20 



Basals form a round cup about twico as wide as liij^li. It boars a 

 wi^ll-ilotitu'il band, and lias an Iicniisplu'rical depression for the 

 attaolimcnt of the column. First primary radials largi-, a little 

 lonjjer than wide, three hexa.i;oual, two lieptat^onal. Second and 

 third [)riniary radials to<i:ether not as large as tlie first. Second 

 ])riniary radials q\iadrangular. about twice as wide as long. Third 

 primary radials very little larger than the second, one lieptagonal, 

 two hexagonal, two pentagonal, axillary, and. in the ray opposite the 

 azygous area, bears ujion each upper slo])ing side two secondary 

 radials, which gives to this ray two arms. In each of the other rays 

 the third primary radial bears, upon each up)per sloping side, a sin- 

 gle secondary radial, which is comparatively large, axillary and 

 bears upon each upper sloping side a single tertiary radial, except, 

 in the ray adjoining the azygous area, where there are two tertiary 

 radials, which gives to each of four rays four arms. There are, there- 

 fore, eighteen anibuhu'rai o])cniHgs to the vault, in this species. 

 The arm formula is 4 , 4 i 2 | 4 • 4. Tlu're is a small intercalated 

 plate above the third primary radial, in the ray on the right of the 

 azygous area, in the specimen illustrated. It is this intercalated 

 plate that makes the third |)riniary radial lieptagonal. We supjjose 

 this featui'e to be abnormal, and. therefore, not of specific imiH)rt- 

 ance. 



There are two ])lates. in each regular iiitcn-adial area, one large, 

 the other small and cut off from all connection with the vault by the 

 union of the radials above. In the azygous area there are eight 

 plates. The first one is in line with the first i)rimary radials and of 

 about the same size. It is followed, in llic second range, by three, 

 plates, and above these there ari< four smaller ones that are cut off 

 from any connection with the plates of the vault by the union of the 

 second tertiary radials above them. 



The vault is nearly as large as the calyx and bears a very large 

 central proboscis. It is covered by numerous slightly convex 

 polygonal plates. 



This si^ecies has its atliniti<'s with I!, (ijjiiiis. which is a twelve 

 armed species, /■>. (iiiiini.riuKtlns. a thirteen armed species. B. rcr- 

 nenilidniis, a fourteen armed s])ecii's, B. raridhilis, a fifteen armed 

 species, B. cofjiitilKs. a sixteen armed species, and B. coiifKiiKjitiiieiis, 

 a twenty armed species. It will be distinguished fr(im these species 

 by the arm formula and eighteen ambulacral <i])enings to tlu' vault. 



