u 



are twelve plates, in some of the arms, on our specimen, and if 

 complete there would probably be as many more. 



This species cannot be confounded, with any other, from rocks 

 of the same age, nor, indeed, with any hitherto described. 



Found in the Keokuk or Warsaw Group, in Clark county, In- 

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



ICHTHYOCRINUS SPINOSULUS, 11. Sp. 



Plate V, Fig. 4, view of a compressed specimen, with part of 

 the spines on the first radials broken off. 



Our specimen is compressed, but the true form with the arms 

 folded is roughly ovoid. Distinct sutures separate the plates. All 

 axillary plates bear a central spine and there are occasional 

 spines on other plates. The entire surface is papillose or very 

 strongly granular. The column is large, round, tapers rapidly 

 from the body and is composed of thin plates. The basals and 

 subradials are entirely covered by the head of the column and 

 have- not, therefore, been observed. There are no interradials. 



Primary radials, three in each series; they gradually widen, but 

 are not of exactly the same length and hence there is a slight 

 interlocking of plates, instead of straight sutures separating the 

 different series. The first primary radials are rather longer than 

 either of the others and each bears a remarkably strong spine, 

 that is directed downward, by the side of the column. The sec- 

 ond primary radials are arcuate in the middle of the upper face 

 for the projection of a lip or flange from the third plates and 

 each bears three small spines, one central and one on each side. The 

 third primary radials have steep superior sloping sides, each bears 

 a strong central knob or short spine, and two small spines, one 

 on each side. They are axillary and bear on each upper sloping 

 side three secondary radials. 



The first and second secondary radials are of about the same 

 size, arcuate, and are produced transversely in a sharply convex 

 central ridge with three obscure nodes on each. The third sec- 

 ondary radials are larger and longer and each bears a very strong 

 central node or obtuse spine, and supports upon each upper slop- 

 ing side a single arm or tertiary series. There are, therefore, 

 twenty aims in this species. Each arm is composed of a single 

 series of plates united by arcuate instead of transverse sutures. 

 The arms are infolded and broken at the superior end of our 



