DOSSILS OF THE BURLIXGTOX GROUP. 425 



them presenting a pentagonal outline, and two hexagonal, 

 (that is without counting a very obtuse angle, doubtless 

 existing at the middle of the under side of each, but hidden 

 by the column). First radials about the size of the sub ra- 

 dial pieces, and pentagonal in form, the upper side always 

 truncated the full breadth. Second radials quadrangular, 

 constricted in the middle, and expanded at the ends ; sepa- 

 rated from each other by spaces nearly half their own 

 breadth, measuring at the middle. Third radial pieces a 

 little longer and narrower than the second, abruptly dila- 

 ted at the ends, and strongly contracted in the middle; each 

 with apparently the exception of one in the anterior ray 

 (which seems to bear only one arm), supporting two arms 

 on their superior strongly sloping sides. 



Anal plates forming a double alternately arranged series, 

 exactly as in #. xcalarix. Arms apparently simple from their 

 origin on the third radials ; composed of pieces as long as 

 wide, or a little longer, and angular on the dorsal side; 

 each piece always contracted in the middle, and expanded 

 at the ends, particularly at one of the upper lateral corners 

 alternately on each side of the arm, for the reception of 

 the pinnule, thus giving the arms a zigzag appearance. 

 Pinnulae rather stout, and composed of pieces about as 

 long as wide. 



Surface of the body with deep indentations at the cor- 

 ners of all the plates, so as to form a comparatively strong 

 ridge radiating to each side of the subradial pieces, to con- 

 nect with a similar one on each of the adjacent pieces. 



Hight of body about 0.11 inch to the top of the first ra- 

 dial pieces, where it measures about 0.17 inch in breadth; 

 length of arms, about 0.95 inch. 



This species is nearly related to S. zealari*, but in addition to being 

 much smaller, it differs in the strong radiating costa? of its body 

 plates, as well as in having its subradial plates merely convex, instead 

 of tumid. Its arm joints also differ in being proportionally longer, and 

 contracted in the middle. 



55 



