Contributions to Invertebrate Palaeontology. 553 



SPECIES FROM THE LIMESTONES ABOVE THE "BONE-BED," IN 



THE VICINITY OF COLUMBUS, OHIO, AND NOT KNOWN 



TO OCCUR BELOW THAT HORIZON. 



ECHIXODERMATA. 

 CRINOIDEA. 



Genus GII.B£RTSOCRI]VlJS Phillips. 



Gilbertsocrinus spiiiigenis. 



Plate XI, fig. 12. 



Trematocrinus spinigenis Hall, 15tli Rept. State Cab., p. 128. 



Gilbertsocrinus {Ti-ernatocrinus) spimgerus Hall, Descript. of New Species of 



Crinoidea from the Carboniferous rocks of the Mississippi valley, plate 



1, fig. 9. 



Body small, of nearly equal height and width, broadly truncated at the 

 base, slightly rounded and expanded in the lower half of the height, but 

 generally contracted above to the base of the arms. The base of the cup is 

 deeply impressed, including the basal and sub-radial plates ; the first radials 

 form the lowest part of the cup, the second radials are placed at the point 

 of its greatest diameter, and the third at about one-half of the entire height. 

 The first and second radials are comparatively large, the first being hepta- 

 gonal, the second hexagonal and the third which are smaller than the second 

 are heptagonal, obtusely cuneiform above, and support on each sloping face 

 two projjortionally large supra-radial plates, one above the otlier, the upper 

 face of the second one of which is excavated and its surface cicatrized for the 

 attachment of the true arms, while the summit arms arise from above and are 

 formed by the junction of the plates from the two adjacent rays. The first 

 interradial plates are moderately large, are truncated below and rest on the 

 upper truncated ends of the subradials, thereby separating the first radials 

 of the adjacent rays from each other. Above the first interradials the plates 

 are in arches of three plates each for two or three transverse ranges with two 

 and then one at the top, except in a single lateral area where there is but two 

 plates transversely. 



The anal area is somewhat larger than the other areas, but the arrangement 

 of plates cannot be determined from excess of silicification. The inter-supra- 

 radial areas are marked by two plates in each, situated one above the other, 

 the second one having its upper end forming a part of the summit or dome of 



Annals N. Y. Acad. Sci., V, Dec. 1890.— 37 



