this arrangement the basal plates, when united, form a 

 diso having eleven sides and abuts upon eight plates, a pecu 

 liarity we have never observed in any otlier fossil. 



The first primary radials are longer than wide, very un- 

 equal in size, two pentagonal, two hexagonal, and one heptag- 

 onal. The radial series are so different that we will describe 

 them separately. The first primary radial that truncates the 

 pentagonal basal plate is the largest plate in the body, heptag- 

 onal, and has a width greater than its length. It is followed 

 by a second primary radial, one-halt smaller than the first, 

 longer than wide and heptagonal. This is followed by a short, 

 small, third primary radial that is heptagonal, axillary and 

 supports upon each superior sloping side a small secondary 

 radial, which gives to this ray two arm oi)enings that enter 

 the vault iiorizontally. In one of the series, supported in one 

 of the re-entering angles of the basal disc, the first primary 

 radial is very large and hexagonal. It is followed by a second 

 primary radial, that is very large, wuder than long, heptagonal, 

 axillary, and supjiorts on one of the superior sides a single, 

 secondary radial, which is axillary and sujijiorts tertiary radials, 

 and upon the other two secondary radials, the last of which is 

 axillary and sujiports tertiary radials, which gives to this ray 

 foui' arm openings to the vault, lliat are directed horizontally. 

 In the other series sup))orted in a reentering angle of the l)asal 

 disc, the first primary radial is mucli smaller than the one 

 last described, longer than wide and p(mtagonal. It is followed 

 by a second 2)rimary radial much larger than itself, wider than 

 long, having eight sides, axillary and supporting, cm the left 

 lateral side a single secondai\y radial that is axillary and suj)ports 

 tertiary radials, and, on the su])ei-i()r si(l(>, a single secondary 

 radial that is not axillary, and, on the right lateral side, a 

 secondary radial that is axillary and supports tertiary radials, 

 which arrangement gives to this ray five arms. It will be 

 noticed here, that the two radial series supported in the re- 

 entering angles of the basal disc' have no third ])rimary radials. 

 In the radial series, on th(! right of th(! azygous area, tlie first 

 primary radial is large, longer than wide, hexagonal, and 

 followed by a second primary radial, which is iiiuch smaller, 

 hexiigonal, and followed by a third ])i-iiii;u-y radial, whicli is 



