43 



tloes not Hppear to be pressed out of shape, tlie arms are pressed 

 together a little, so as to make them thinner, laterally, than they 

 should be. The plates preserved in our specimen are longer tiiau 

 wide. The first azygous plate is more than twice as long as wide, 

 rests in a notch between two first radials, truncating the one on 

 the right more than the one on the left, and extends nearly to the 

 top of the second radials. It is followed by two plates, the larger 

 one extending down, on one side, one third the length of the plate, 

 and the smaller one truncating the upper side. These two plates 

 are followed by a triangular plate that reaches nearly to the top 

 of the third radials. 



The peculiar, fiattened calyx, subpyramidal, angular and beveled 

 plates and arrangement of tlie azygous plates distinguish this from 

 all other described species. 



Found in the Keokuk Group, at Button Mould Knob, Kentucky, 

 and now in the collection of Wm. F. E. Gurley. 



Family IC'HTHY0CRINID.E. 



ichthyockinus olaekensis, n. sp. 

 ritiir 11", Jf/g. .") , /ate)-(tl rific of <i c(i})i})vesseil sprei men. 



Species small. Our specimen is compressed, but the general 

 form with the arms folded is sul)ovate. The plates are free from 

 spines and nodes; the sutures are very distinct and slightly arcu- 

 ate, the superior plates generally overlap the inferior ones in the 

 middle part. The column is very large and entirely covers the 

 basals and subradials so they have not been observed. There are 

 no interradials. 



There are three primary radials in each series. They widen 

 rapidly and are subequal in length. The different series interlock 

 instead of having a straight separating suture. There are four 

 secondary radials in each series of about the same length, and 

 each plate has about the same length as a primary radial, they 

 expand very little, so that the fourth or axillary plate is not 

 much wider than the first plate. The different series interlock in 

 the same manner that the primary series do. The fourth plate 

 supports upon each upper sloping side a single non-bifurcating 

 arm, which gives to the species twenty arms. The arms are com- 

 posed of short quadrangular plates, with arcuate sutures. There 



