17 



Basals short, twice as wide as high, standing upright and 

 longitudinally marked with three or four delicate stripes. 



First primary radials the larger plates of the body, as long 

 as wide, slightly convex, and bearing a delicate ridge directed 

 toward each adjoining plate. Second primary radials, less than 

 half as large as the first, hexagonal, and ornamented with deli- 

 cate ridges. Third primary radials about as large as the second, 

 pentagonal and hexagonal, ornamented with delicate radial 

 ridges and bearing upon each upper sloping side a single second- 

 ary radial, which, in turn, supports upon each upper sloping 

 side two tertiary radials. There are twenty arm openings to 

 the vault. 



Regular interradials six. First one smaller than a second 

 primary radial, it is followed by two smaller plates and these 

 by two still smaller ones and these by a single plate, above 

 which a long narrow plate unites with the plates of the vault. 



There are ten plates in the azygous area. The first one is in 

 line with the first primary radials and of the same size and 

 sculptured in the same manner; it is followed by two plates of 

 about the size of the second radials, and these are followed by 

 four smaller plates, and these by two plates and these by a 

 single plate that unites with an elongated plate that connects 

 with the plates of the vault. 



The arms are very long and comparatively coarse and com- 

 posed of a double series of interlocking plates. Pinnules dense. 



Distinguished by the delicate sculpturing and number of inter- 

 radial and azygous plates. 



Found in the Burlington Group, at Burlington, Iowa, and 

 now in the State Museum, at Springfield, Illinois. 



ERETMOCRINTJS LYONANUS, n. Sp. 



Plate III, Fig. 1, basal view of a specimen crushed, with pro- 

 boscis down and arms expanded, on the surface of a rock. 



Calyx short, below medium size; plates thin, slightly convex 

 and smooth. The basal plates and some in each radial series 

 are destroyed, in our specimen, so as to make an accurate de- 

 scription of all of them quite impossible. The first primary 



-3 G. 



