FOSSILS OF THE BURLINGTON GKOUP. 361 



radial, and so on, so that each of the main divisions of each 

 ray throws off alternately on each side three (occasionally 

 four on one side) arms, making about twelve arms to each 

 ray, or sixty or more to the whole series. 



Anal pieces ten to twelve ; the first one nearly as large 

 as the first radials, hexagonal in form, and surmounted in 

 the second range by two smaller pieces, above which there 

 are four in the third range, and over the latter three or 

 four other small pieces are irregularly arranged. Interra- 

 dial pin - -< ven to eight to each area, the first being about 

 the same size as the second radials, hexagonal in form, and 

 supporting two smaller pieces in the second range, over 

 which are two others in the third range, and above the 

 latter, some three or four small unequal irregularly ar- 

 ranged pieces may be usually counted. One or two very 

 small pieces are also usually seen in each axillary space. 



Arms, as usual in the genus, rising from the margins of 

 the expanded disc, very slender, rather long, and not taper- 

 ing, excepting near their immediate extremities ; composed 

 of very small alternating pieces, each one of which bears a 

 pinnule at its outer extremity. Pinnula? delicate, long, 

 crowded, and composed of joints apparently three or four 

 times as long as wide, and each bearing on its upper margin 

 a small flattened, triangular process, or short compressed 

 spine, that laps upon the next pinnule above, in such a 

 manner as apparently to have prevented the free expansion 

 of any one pinnule when not accompanied by a simultane- 

 ous movement of all the others on the same side of each 

 arm. 



Vault depressed convex, composed of small, slightly con- 

 vex, unequal, irregularly arranged pieces, ventral tube sub- 

 central, being slightly nearest the anal side, slender, and 

 rising abruptly from the vault, which does not slope up to its 

 base. 



Surface presenting a more or less rough appearance, 



