FOSSILS OF THE BTJELINGTON GROUP. 457 



but broadly and rather deeply excavated; basal plates con- 

 vex or slightly tumid over most of their surface, and curv- 

 ing upward above the middle, to the somewhat constricted 

 suture separating them from the radials above. First ra- 

 dial pieces a little longer than wide, usually somewhat 

 wider above than below, and having a general oblong out- 

 line, though the superior lateral angles are obliquely trun- 

 cated to form notches for the reception of the interradials, 

 and the lower margins are slightly rounded in outline ; all 

 convex or rounded over from side to side, on the outer sur- 

 face, so as to give, with the deeply excavated sutures 

 between, an obtusely lobed appearance to the body, as seen 

 from below; facet for the reception of the second radial 

 pieces equaling about half the breadth of the upper part 

 of the plates, and excavated less than one-third their length 

 downward, at the middle on the outer side. Second radial 

 pieces very small, or only showing a small triangular outer 

 surface, and allowing the first of the succeeding pieces to 

 rest with near one-half of their under surface directly down 

 on the first radials. 



Kays, after the first division on the second radials, divi- 

 ding on the second pieces, the outer division giving origin 

 to an arm, and the inner division bifurcating again on the 

 second pieces, so as to form two arms, thus making six 

 arms to each ray, or thirty to the whole series. Arms long, 

 slender, and directed upward from their bases, the lower 

 pieces and second radials not being much curved outward ; 

 all slender below, and increasing slightly in thickness to 

 near the middle, thence tapering very gradually to their 

 extremities; dorsal or outer surfaces of each somewhat 

 rounded, and lateral surfaces flattened, or sometimes even 

 slightly furrowed. Arm pieces, as usual, consisting of a 

 single wedge-formed series near the base of the arms, but 

 HTM dually passing into a double interlocking series of pieces, 

 which, fHrther up, near the middle, are very short, and each 



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