27 



area aijipurts. (in cai-h ii))]M>r slopiiiLj siilc tliree secondary ralials, 

 wliicli u:ivcs to this i-ay two anus. In cacli of tlie lateral rays and 

 in the ray oti the riglit of the azygoiis area tlie third primary radial 

 supports, upon one upper side, three seeoudary radials and upon tiie 

 other two. the last one beinji' axillai'v and supporting, on eaeli upjjer 

 side, two tertiary radials, which gives j^to each 'of these rays three 

 arms. In tlie ray on the left of the azygous area the third i^rimary 

 radifd bears, upon each upper sloping side, two secondary radials, 

 the last being a.xillary and supporting, on each upper sloping side, 

 two tertiary radials, which gives to this raj' four arras. There are, 

 therefore, fifteen arms in this species. The [arm formula is 3-(-B-|-2 

 +4-1-8. 



In each regular interradial area, tliere are three plates, one in the 

 iirst range followed by two elongated plates, in the secoud range^ 

 that unite with the plates of the vault. In the azygous area there 

 are seven jtlates. The first one is in line with the first primary ra- 

 dials and about the same size. It is followel by three ]olates, in the 

 second range, and these by three plates, in the third range, all three 

 of which unite with the plates of the vault. 



Vault jtyramidal by reason of the depressed interradial areas, 

 larger than the calyx, and bears a large central proboS(n's. It is 

 covered by large convex, polygonal plates. 



This species is most nearly related to B. rrsercdius. above de- 

 scribed, from which it is distinguished, by the hexagonal disc, form- 

 ed by the basal ]>!ates. instead f)f a round expanding cup; by the 

 azygous area, which has seven plates, three of which unite with the 

 j)lates of the vault, instead of four plates, only one of which con- 

 nects with the vault; by the larger \auU which is covered with 

 larger and more convex plates; and by the arm formula which is 

 3+3-f 2+3 4, instead of 3 4 2 3 3. There are minor differ- 

 ences as may be seen by comparing the descriptions. It need not 

 be compared with any other species. 



Found by K. A. Blair, in the Burlington Ciroup, near Sharon, in 

 southwestern Missouri, and now in the collection of S. A. Miller. 



