134 Cincinnati Society of Natural History. 



velopment of the frontal margin of the shield. In all other respects 

 (if we except its larger size) much resemblance is presented to C. ni- 

 agaraensis, Hall. The differences between the two are, however, suf- 

 ficiently marked, and there can be but little danger of confounding 

 one with the other. 



Formation and locality: a rare species occurring in the lower beds of 

 the Niagara Group, at Osgood, Ripley county, Indiana. 



Collectors: J. Ralston Skinner, C. Mullalley, E. O. Ulrich. 



DE8CBIPTI0NS OF NEW SPECIES OF CRINOIDS. 

 FR03I THE KASKASKIA GROUP OF THE 

 SUBCARBONIFERO US. 

 By A. G. Wetherby, 

 Prof, of Geology and Zoology, University of Cincinnati. 

 The crinoids described in this paper were collected by me, in 

 subcarboniferous rocks of the Kaskaskia Group, in Pulaski county. 

 Kentucky. The genus Pterotocrinus was fully discussed in a previ- 

 ous article, and its relationships made out so far as the specimens 

 permit. The unequaled preservation of these fossils has made their 

 specific identification an easy task. 



Pterotocrinus acutus, u. sp. 



[Plate XI., fig. 2a upper, 2b basal, 2e side view, natural size.] 



Basals — Two, pentagonal, centrally excavated dorsally and laterally 

 for the reception of the slender column. Their line of junction, produced, 

 passes through the center of the latter, of the azygos plate, between 

 the inner edges of the first radials on the azygos side, and through 

 the center of the first radial upon tlie opposite side. These plates are 

 thickened and slightly carinated at the outer edges of the columnar 

 excavation. 



Radials — First series five, the two on the azygos side heptagonal, 

 wider than high, laterally excavated inwardly for the reception of the 

 convex sides of the az^-gos plate, above the apex of which the}' unite, 

 completely inclosing it. 



The opposite, or anterior first radial is heptagonal, wider than high, 

 with a slight central angle on the basal side. It is excavated on the 

 opposite face for the reception of the small second radials, which meet 

 in a line over its center. 



The other two first radials are hexagonal, wider than high, and 

 uearl}' like the last, except that tliey join the basal by a single side. 



