15 



these rays four arms. In the ray opposite the azygous area the 

 third primary radial bears upon each upper sloping eide three 

 secondary ratliais wliich gives to this ray two arms. There are. 

 therefore, in this species, sixteen arms and sixteen ambulacral 

 openings to the vault. 



There is a single large tumid plate in each regular interradial 

 area. In the azygousarea there are six plates. The first one is as large 

 as a first primary radial, and in line with them, and bears equally 

 as robust and cuneiform a spine. It is followed by three much 

 smaller plates, in the second range, and these, in turn, by two 

 plates, the lower one of which is much the smaller. 



The vault is conical, larger than the calyx and bears a subcen- 

 tral proboscis. It is covered with large subspinous plates. There 

 is an elongated plate between each pair of arms and one dividing 

 the three armed rays that separate the ambulacral coverings at 

 the base of the arms and a pore penetrates tlie vault at each in- 

 ferior angle of these narrow- plates, which arrangement gives to 

 this species eighteen of these so called ovarian apertures. 



This species is distinguished by the general form, tumid plates 

 on the lower part of the calyx and smooth plates in the superior 

 part, azygous area and sixteen arms. 



Found by Prof. A. G. Wetherby in the Keokuk Group, of Ten- 

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



li.\TOCRINUS CASUALfS, n. Sp. 



Plalc I, Fig. 17, vieio opposite the azyyons area: Fig. IS, azij- 

 goiis view of same specimen. 



Species below the average si/.e, biturbinate, vault and calyx sub- 

 equal. Calyx broadly truncated below, only slightly expanded 

 above and ambulacral openings directed upward at an angle of 

 forty degrees. Diameter about one fifth greater than the height. 

 Eadial ridges not distinguished. A few of the plates in the lower 

 part tumid, those in the upper part only slightly convex or plane. 



Basal plates stai:d upright and form an hexagonal disc three 

 times as wide as high, truncated below, and having a deep cavity 

 for the insertion of the column, which is a little less than half 

 the diameter of the basal disc. Columnar canal small. Fir»t pri- 

 mary radials large, one-fourth wider than high, three hexagonal, 

 two heptagonal and each bearing a robust, transverse node. Sec- 

 ond primary radials small, quadrangular. Third primary radials 

 a little larger than the second, pentagonal and axillary. The sec- 

 ond and third primary radials together much smaller than the first. 



