OF ARTS AND SCIENCES. 21 



lai'ly-sided octagon. The columnar pit is shallow, oval ; columnar 

 facet obscurely pentagonal ; perforation small and round. The pieces 

 are prominent near the line marking their junction to those resting 

 upon them, being suddenly reflected upward. 



Radial pieces five, subquadrangular, the largest as wide as high, 

 diminishing in size from the anterior piece on either side to the anal 

 piece, swelling from the base and sides toAvard the superior margin, 

 irregularly truncated above, slightly depressed at the summit between 

 the pieces. 



Second radials. Fragments of the second radials are attached to 

 some of the first radial pieces ; they are minute, and rise within the 

 superior margin of the first radial pieces. The precise form of the 

 second radials is not known. 



Inter-radials. Between each group of arms, resting in the depres- 

 sion between the radials, is a single piece, usually pentagonal in form ; 

 it rises nearly as high as the opening into the body at the arms. 



Anal pieces. Rising from the deepest angular notch at the junc- 

 tion of the basal pieces, is a large piece, the lower part of which is 

 similar in form to the first radials, rising higher than they do ; the 

 upper margin is horizontally truncated about one third the breadth 

 of the piece ; the sides above the radials angularly sloping toward 

 the top of the radials on either side ; the centre of this piece supports 

 one, and the sloping sides each support a piece of the second range 

 of anal pieces ; those on the sides correspond in size, form, and posi- 

 tion, to the inter-radial pieces above described. These are again suc- 

 ceeded by a third range of pieces, triangular in form, three in number, 

 the central one of which reaches the mouth (?), which is surrounded 

 by three additional, small, long, narrow pieces. The series of pieces 

 under the mouth are slightly depressed above the second i^ange. 



Summit. The summit above the radials recedes a considerable 

 distance within the upper margin of the calyx. It is covered by 

 numerous small polymorphous pieces, six of which are spinigerous ; 

 the largest and most prominent of these occupies the centre of the 

 summit, immediately in contact with the pieces surrounding the mouth; 

 the other pieces forming the second series of those rising above the 

 openings into the body at the arms. The two spinous pieces above 

 the arm-pieces of the postero-lateral rays form a circle around the 

 central piece, the anterior part of the summit having one more 

 range of pieces above the arms than above those arms on either side of 



