356 PALEONTOLOGY OF ILLINOIS. 



on its outer sloping side, a series of about three brachial 

 pieces, the last of which supports an arm, and on the inner 

 sloping side a tertiary radial, giving oif on one side a suc- 

 cession of brachial pieces leading to an arm as before, and 

 supporting on the other sloping side a quaternary radial, 

 and so on, until each main division of each ray has thrown 

 off six or seven alternating arms, thus making twelve to 

 fourteen arms to each ray, and sixty to seventy arms to the 

 whole series. 



Anal plates, about twelve to fourteen, first anal nearly 

 as large as the first radials on each side of it, longer than 

 wide, and hexagonal in form ; above this there are two 

 other smaller pieces in the second range, and three in the 

 third and fourth, with a few very small irregularly arranged 

 pieces above the latter. Interradial plates, nine or ten to 

 each area, first one hexagonal, and bearing two smaller 

 pieces in the second, third and fourth ranges respectively. 

 Arms unknown, vault forming less than one-fourth the en- 

 tire hight, composed of very unequal, irregularly arranged, 

 more or less tumid pieces. Ventral tube, or so-called pro- 

 boscis, large, very long, slightly tapering, and composed of 

 small pieces usually wider than long, and more or less 

 angular on the outer side ; sometimes (perhaps abnormally) 

 recurved at the extremity. 



Surface of body plates ornamented with very distinct, 

 compound, radiating costse, which unite 011 the prominent 

 middle of the plates, so as usually to form sharply angular, 

 transverse or arched ridges, the whole presenting a very 

 rough but neatly sculptured appearance. 



Hight of a medium-sized specimen to the base of the 

 ventral tube, 0.85 inch ; breadth of body just below the ex- 

 panded summit, 1.15 inches. Length of the ventral tube of 

 a somewhat larger specimen, 4.67 inches to the broken end ; 

 breadth of same at base, 0.56 inch ; ditto of same at the 

 broken extremity, 0.32 inch. 



