DESCRIPTION OP SPECIES CRINOIDEA 279 



This species was described by Hall from incomplete specimens found in 

 the Burlington limestone. It is not a common species in that formation 

 and when found is almost always as detached plates. These plates are 

 especially characterized by their deep undulations or corrugations and 

 their thin margins, the extreme thinness of the margins being accountable 

 for their usual separated condition when fossilized. In the Fern Glen 

 beds the species is known from only two separate radial plates, the largest 

 of which is here illustrated, which seem to differ in no essential respect 

 from Burlington limestone specimens. 



BARYCRINUS sp. 



Plate 11, figure 22 



This species is represented in the Fern Glen collections by a single 

 specimen, which consists of the base and two radial plates. The under- 

 basal plates are small, being wholly covered by the first column joint — 

 an unusual condition in the genus. The basal plates are moderately 

 tumid and are marked by fine granulations, which are arranged in a 

 somewhat radial manner from the centers of the plates. The radial 

 plates are more than twice as large as the basals, much broader than long, 

 rather strongly convex, and with large arm facets. 



The genus Barycrinus has not hitherto been recognized in beds older 

 than the Lower Burlington limestone. This species is entirely different 

 from any of those in the Lower Burlington and is probably new, although 

 the specimen is too incomplete for description. 



POTERIOCRINUS sp. 



Plate 11, figure 24 



This specimen is a small, complete dorsal cup with the base excavated 

 for the attachment of the column. The width of the cup at the rim of 

 the basal truncation is slightly more than 2 millimeters, the width at the 

 top of the radials 7 millimeters, and the total height 5 millimeters. The 

 sides from the basal truncation to the tops of the radials are slightly con- 

 vex; all of the plates are smooth. The underbasals extend beyond the 

 columnar facet for about one-half of their length; the basals are wider 

 than high and are smaller than the radials. The arm facets occupy the 

 entire width of the radials distally. Both an anal and a radianal plate 

 of nearly equal size are present, as well as the first tube plate, which is 

 slightly smaller. 



So far as it is preserved, this little species is not unlike several mem- 

 bers of the genus which have been described from the Kinderhook and 



