18 



This species is distinquished by its form, large azygous area 

 connected with the vault, and peculiar azygous interradius on 

 the vault, and eighteen arms. It cannot be mistaken for any 

 species heretofore described. 



Found by Prof. A. G. Wetherby in the St. Louis Group, in 

 Washington county, Indiana, and now in the collection of Wm. F. 

 E. Gurley. 



BATOCEINUS PILEUS, n. sp. 



Plate II, Fig. 0, basal view slightly brolcen; Fig. 7, summit view; 

 Fig. S, side vieio of the same specimen. 



This species is rather large in circumference, with an almost 

 flat calyx and moderately convex vault, or plano-convex in outlinp. 

 The cap-like form suggested the specific name. While the calyx 

 is nearly flat, the radial ridges are distinctly convex. Ambulacral 

 openings directed upward at an angle of thirty degrees and not 

 visible in a basal view. 



Basal plates form a flat disc very little larger than the diame- 

 ter of the attaching column. First primary radials short, more 

 than twice as wide as lou.t4-, three hexagonal, two heptagonal. 

 Second primary radials about two-thirds as large as the first, quad- 

 rangular. Third primary radials nearly as large as the first, pen- 

 tagonal, axillary, and supporting on each upper sloping side two 

 secondary radials. The second secondary radials are axillary and 

 bear upon each superior sloping side three tertiary radials which 

 gives to each ray four arms. There are, therefore, twenty arms 

 in this species and twenty ambulacral openings to the vault. 



There are three plates in each regular interradial area, one mod- 

 erately large followed by two smaller ones. The azygous area is 

 subovate in outline and contains eiglit plates. The first one is in 

 line with the first primarj' radials and narrower and longer than 

 either of them. It is followed by three plates in the second range 

 and three in the third range, the middle and higher one of which 

 is truncated by a small plate that extends to the top of the calyx 

 and unites with the plates of the vault. 



The vault is convex and twice as large as the calyx, most tumid 

 opposite the azygous side. There are three large, convex plates 

 over each ambulacral area, one over the place where each pair of 

 ambulacral furrows unite and the other over the point where they 

 all come together. There are also four or more large, convex 

 plates near the base of the proboscis on the side opposite the azy- 

 gous area. The interradial areas are slightly dejjressed and cov- 



