362 PALAEONTOLOGY OF ILLINOIS. 



owing to the tumid character of the body plates, of which 

 the first radial and first anal pieces are the most prominent. 

 In some instances all the radial pieces project in the form 

 of a prominent transverse node, and the anal and interra- 

 dials more frequently as rounded nodes. The smaller ter- 

 tiary and succeeding supplementary radial and brachial 

 pieces are merely convex. Sometimes, there are faint indi- 

 cations of very short ridges at the immediate sutures, 

 between the first radial pieces and the bases, as well as at 

 the sutures between the other primary radials. 



Hight of the body of a medium sized specimen to the 

 horizon of its arm bases, 0.90 inch ; do. to the top of vault 

 from base, 1.20 inches ; breadth of expanded vault, between 

 the rays, 1.40 inches; do., to the extremities of the rays, 



1.60 inches. 



i 



This species will be distinguished from others yet known of the sec- 

 tion provided with a proboscis, by its very tumid or iiodose body plates 

 without costse, by the number of its arms, and more spreading disc, and 

 other details. Although the two divisions of each of its rays project 

 somewhat beyond the margins of the disc, so as to give it a ten-angled 

 outline, as seen from above or below, they are not near so much pro- 

 duced as in the last described species. 



The specimens of this species figured and described by Prof. HALL, 

 which are now before us, have lost the arms, though they give a good 

 idea of the structure of its body. The beautiful specimen we have 

 figured, although having its body somewhat crushed, and its base broken 

 away, is interesting as it shows the delicate arms and pinnule. We 

 have seen no example of this species with ventral tube, or so-called pro- 

 boscis, preserved. It was evidently very slender, however, even at its 

 base, and rises very abruptly from the depressed convex vault. 



Locality and position Upper bed of Burlington division of the Lower 

 Carboniferous series. The specimen figured No. 50 of Mr. WACHSMUTH'S 

 collection. 



